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FAQs on Brackish Water (mostly terrestrial) Crabs, other Crustaceans

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Red Claw Crab and salt      2/23/15
I tried to find a similar post on your site sorry if this has already been addressed.
My dad put together an aquarium for my kid and i wanted a crab, well i wanted a blue crayfish but those were $25 and the crabs were $3 and they were equally as cool if not more so.
<Quite so. Land crabs are nifty animals in lots of ways.>
ANYWAY i did do research beforehand and i DID know brackish is preferential if not essential.
<Something like that. Since these crabs are essentially amphibious, assuming the "land" is somewhere humid and warm they only spend part of the time underwater. Brackish water probably helps them, in the long term, but yes, they do seem to live many months with just access to freshwater. That said, their distribution in the wild is apparently coastal rather than inland. Their full common name, "Red Claw Mangrove Crab", is probably accurate, and being cynical for a moment, the missing word "mangrove" surely wasn't dropped accidentally by the exporters!>
Depending on who you ask.
<Indeed, the scientists who collect them versus the people selling them in pet stores!>
Well i got her anyway, as the petstore carrying them was keeping her in a cramped freshwater tank. So i justified putting her in my tank and opposed to the petstore or some more ignorant owner.
Now, more to the point, i was sitting on the floor staring at her for a while and i noticed a bag of rock salt next to me. Being the weirdo i am i shoved some in my mouth and then thought maybe i can give the crab some.
<Sure! Provided that salt is not iodised, it should be fine. Not as good as marine aquarium mix, but better than no salt at all.>
So the question is, can i give some to the crab?
Can i safely put a chunk on her rock and have her not die?
<No, you can't stick a chunk in the tank!
Grab a cheese grater or a chisel, grind off or chip away some bits, allowing 6 grams per litre/3-4 teaspoons per US gallon. So if you have a 3 gallon bucket, then 9-12 teaspoons of salt is about right. That will create slightly brackish conditions (for reference: full seawater is 35 gram salt per litre, so what you're making is about one-sixth normal seawater salinity). Dissolve salty chunks in water completely before adding to the aquarium! Now, each time you do a water change, you can replace plain freshwater with a bucket of this slightly brackish water.>
It seems relatively safe and possibly beneficial to give her some to satisfy her dietary needs.
<Dietary needs are primarily protein and calcium! Bits of white fish fillet, unshelled shrimps, and even things like cooked peas and soft fruit. Iodine is the missing thing here, and a prime cause of deaths with crabs. You can buy "crab food" that contains iodine, but it's cheaper and easier to grab some iodine vitamin supplement as used in marine tanks, and dose at one-half the amount recommended on the bottle. Some "sea vegetables" are iodine rich including Sushi Nori and other seaweeds you can pick up in Asian food markets.>
But im no expert on crustaceans (though i do have a 17 year old hermit crab) Would this be a terrible idea?
<Dumping a sodium chloride lump in the aquarium would be catastrophically bad.>
Do you think she would know to "lick" it? Could she "lick" too much and die? I figure she'd be fine since she's in the water most of the time. Are they're any other options to satisfy her salt needs? Maybe a small dish with saltwater in it on her platform?
<Now you're thinking right!>
Thanks for any input.
<Most welcome, Neale.>

My red claw crab is missing 2 legs      5/27/13
I purchased a red claw crab yesterday at a local fish store and i was feeding the fish tonight and noticed that my crab had 2 legs missing on one side he is still getting around the tank ok and he is eating but will his legs grow back or will he die?
<These legs can be regenerated, through successive molts, IF the conditions are propitious here. A lack of predatory tankmates, enough food, alkalinity and calcium, land to get out of the water, scavenge about on... Read here:
and the linked files above; esp. re foods/feeding and systems. Bob Fenner>

Red claw crab (Perisesarma biden), comp., fdg., beh.   4/17/13
Hello again WWM, I have a 29 gallon tank (about 40% land, water is 4 inches deep at deepest point, sand substrate, brackish water, heater that keeps it 80 degrees during the day, 76 at night, quite humid, plenty of slate rocks, 6 good size grasses in and out of water, hang-on 15 gallon filter that I've modified to work as a waterfall) with 6 crabs (3 females, 2 males and one I haven't checked) in it.
<All sounds good.>
I have a couple questions that I can't seem to find any answers to. First of all one male crab is getting ready to molt and is missing both claws.
<Likely fighting; what these crabs do; isolate the victim if at all possible.>
Will he be able to eat at all without them?
Is there anything I can do to help him if not?
<Could try hand feeding, but crabs aren't real smart, so could be tricky.
Possibly crab will have new claws after moult, but if not, will need feeding.>
Also after reading I'm going to pick up an iodine supplement as soon as possible, but the store is quite a trip. Can the iodine in potatoes provide any help for them in the meantime?
<Some, if they could digest potatoes, which I doubt. Sushi Nori and most seafoods will be better.>
I have included them in their diet along with bloodworms, banana, and occasional orange and avocado.
<All sounds ideal.>
They seem to enjoy them but is this just a wasted effort on my part?
My final question would be is it normal that none of the crabs are burrowing?
<Normal. These crabs prefer to climb, when they aren't killing each other anyway.>
They are all quite active (except the one close to his molt) but I want to make sure this isn't a sign of bad conditions. Thanks for your great information and responses, AA
<And thanks for the kind words. Cheers, Neale.>

Brackish water crab    10/24/12
Hello. I am planning on dedicating my 135 gallon aquarium to brackish water crabs. It is 72 x 18 x 24 inches high. I am planning on having land and water sections so I can keep a variety of crabs. How many could I keep in this aquarium? What parameters should I keep the aquarium at? I know I want red clawed crabs (Perisesarma species) and fiddler crabs (Uca species) with a few others I may find interesting. What other crabs would do well with these? Lastly, what would be your recommendation as to a set up for my aquarium (substrate, heater, decorations, etc)? Thanks for taking the time to answer my questions!
<You could probably keep dozens of small crabs in a tank this size… but Red Claw Crabs and in fact most other crabs don't necessarily work well in groups, and mixing species is almost never a good idea. A certain amount of "attrition" is likely as dominant crabs attack weaker ones. Having big groups probably helps in the same way as it does with Mbuna and other aggressive animals, but still, there'll always be a certain degree of risk. But there are two workarounds worth suggesting. The first is Thai Micro Crabs. You'd only need a very small aquarium for these (even 10 gallons) since they're pretty peaceful and all they really need from the keeper is lots of floating plants (they prefer to hang upside down from such plants). Alternatively, consider Fiddler Crabs. The males are mostly bluffers rather than fighters, so if they're given enough space, serious fights are normally avoided, especially if you have ensure each male has a safe burrow (or cave) it can retreat to. Fiddlers and Red-Claws shouldn't be kept together for the same reason -- Fiddlers lose out, and the Red Claws treat weak specimens as live food. The big plus with Fiddlers is that they can work well Mudskippers or, if you prefer to maintain a reasonable depth of water, salt-tolerant livebearers such as Guppies and Mollies. Since your aquarium is quite large, setting up a half-water, half-land system shouldn't be difficult, so keeping Fiddlers with Mudskippers and/or livebearers should be easily do-able. Oh, and one last idea. Why not go marine? Mantis Shrimps for example are even more fun than crabs, and you could use dividers to maintain several specimens in one tank. But even with regular shrimps, crabs and lobsters, there's plenty of variety that could all live together. A marine aquarium set up with live rock and just various crustaceans would be easy to maintain and relatively inexpensive (without the fish, you shouldn't have any real problems maintaining adequate water quality). Cheers, Neale.> 
Re: Brackish water crab, other BR Livestocking     10/25/12

Hey Neale. Since getting your reply I've been researching tank mates for the 135 gallon. I would like your opinion on the tank. I am planning on getting *Uca crassipes* as the crab.
<A good species.>
As for the tank mates, I am considering the following: *Brachygobius nunus,*
<Yes, but could be eaten by much larger tankmates, so be careful.>
violet goby,
<Yes, but it is quite big, and needs a good 55 gallons of water.>
Celebes Rainbowfish,
<Despite often being reported as brackish-water fish, Celebes Rainbows are not, and don't make sense in this sort of moderately brackish system.>
and Anableps.
<Possible, but do research this species thoroughly. It is challenging and does get rather large (so could, conceivably, view the smaller fish as food).>
As for plants, I am going to get the red mangrove and water sprite.
<Doubt the Water Sprite will tolerate high salinity for long. Plastic plants make a lot of sense, along with (possibly fake) bogwood roots and branches.>
Finally, I am going to keep the water parameters at 25 to 26 dC, 7.5 to 8.0 pH, 16 to 18 dH, and a SG of 1.005 to 1.015.
<This is quite a range of specific gravities! I'd pick a value that makes sense for the community you want, say, SG 1.005 or 1.010, and stick with it.>
I am planning this as a mangrove set up, hence the mangrove fiddler crab, so if any of these fish are not native to mangrove swamps/forests, please tell me.
<Fiddlers and Mudskippers for sure. Violet Gobies and Anableps are more mudflats and tidal estuaries, but could appear in such areas around mangroves. Bumblebees mostly live in rainforest streams, whether brackish or not.
Keeping this in mind, which mudskipper would you recommend? I also need your advice as to how many of each of these I could house comfortably in my 72 x 18 x 24 inch high aquarium.
<Look at the Indian Dwarf Mudskipper, Periophthalmus novemradiatus.
It's a small fish, around 6 cm/2 inches in length, and because it's small, you could keep a large group of 6-8 specimens at least, and in a big group aggression problems will be minimised.>
<Welcome, Neale.>
Re: Brackish water crab 10/25/12

Okay Neale, a couple more questions. If I were to keep *Anableps anableps, * *Gobioides broussonnetii, *Periophthalmus novemradiatus, and Uca crassipes, how many of each would I be able to house comfortably?
<Difficult to say with fish like these in a system with less water than it's gallons would suggest. You say it's a 135-gallon tank; let's assume it's only half filled, and that half will be as much rocks as water. So tops, we're looking at around a quarter that gallonage, or around about 30-35 gallons. Not a huge amount of water, I think you'll admit. Still, for small gobies like BBGs, together with the largely amphibious Uca and Periophthalmus species, that's a lot of space. A dozen BBGs could probably fit into that amount of space together with the Fiddlers and the Mudskippers. But add the bigger fish to the equation and things can really complicated, really quickly. Anableps basically need a big tank (they get to 15-20 cm/6-8 inches or so in length) but with a flat "island" in the middle covered with just enough water for them to beach themselves. Sounds odd, but if you can imagine Shamu beaching himself at Seaworld, that's pretty much what Anableps like to do. Yes, that fits in nicely with Mudskippers, but only if you have huge amounts of space, like in a public aquarium. Realistically, your Mudskippers will be terrified of such big fish as Anableps (on the whole, fish and Mudskippers don't mix, with the exception of species like small Gobies and Guppies that simply don't pose much threat).>
What about without Anableps anableps? I am still looking for a mid-swimmer.
Can you suggest one that can be found in mangroves?
<Shortfin Mollies would work, though they might be slightly too big and so scare the Mudskippers. Guppies, including Endlers can work very well (though big Mudskippers might view small Guppies as live food).>
Do I even need one in this tank?
<Ideally, no. The thing is that Mudskippers don't enter water where they see fish, at least, not big fish. They're not good swimmers, and their defence is to stay out of the water when they see fish, and to jump into their burrows when they see land predators. They don't really swim much, if at all. So, the best Mudskipper tank is set up just for them, and trust me, they're such smart, active fish you really don't need any other fish. Some folks add Guppies, as much as live food as extra colour, any baby Guppies being occasional snacks for the 'Skippers.>
What type of filtration do you suggest?
<If simply Mudskippers, then "cheap and cheerful" is fine, because they're mostly on land anyway, and have a high tolerance for ammonia. A decent sponge filter could be more than adequate, but otherwise an internal canister. What you don't want are pipes or overflows hanging out the tank because Mudskippers WILL find them and escape through them.>
Will I even need any with the red mangroves?
Oops, that's a few more than a couple. Anyways, I want this to look aesthetically pleasing to the eye with a lot of activity and movement.
Would you suggest putting some *Brachygobius nunus* in instead of Anableps anableps? (even though *Brachygobius nunus *aren't from mangrove swamps. I don't mind, as long as there is activity and movement.)
<Anableps is a difficult fish, so yes, I'd recommend looking into their needs and setting up a tank just for them. They're nervous, skittish, and don't do well unless you plan around them carefully (they're not delicate at all, but easily killed through poor planning). BBGs are very low-key fish, so if colour and movement is what you want, then Mollies or Guppies would surely be the better bet.>
Last question: Where would this put me as far as stocking? (As in with *Brachygobius nunus, **Gobioides broussonnetii, *Periophthalmus novemradiatus, and Uca crassipes, how many of each would I be able to house comfortably?) Just exploring my options. Thanks again for your time and speedy responses!
<Do see above. Cheers, Neale.>
Re: Brackish water crab - 10/27/2012

Okay, I don't know how this happens, but I thought of a few more questions as I was reading your reply. This time it is a few. First, since I'll be getting Red Mangrove *Propagules* (seeds) and because they grow slowly, I think I'll get a small filter. Second, (actually the first question), what type of rock would you suggest I put in there for the 'Skippers?
<Whatever you want. Avoid rocks with metallic seams though.>
(Sorry, just had to.) I was thinking live rock, but then thought of the mudskippers and their soft(?) bellies versus the porous rock and discarded the idea.
<Live rock will die in anything less than full marine.>
I would like something native to Mangals. (Found that term online. Means "Mangrove Biome, I think.) Second question: would it be possible to create a catty corner beach slope to try and separate Red Clawed Crabs from Fiddler Crabs?
<Can't imagine they'll stay apart unless completely divided. Crabs climb and burrow.>
(Sorry, just can't get the idea out of my head for some reason!) Third, would violet gobies scare the mudskippers?
Here's what I'm thinking (4 options):
Option 1:
1 to 2 dozen BBGs*
a few fancy guppies (for color/activity and occasional live treat for 'Skippers)*
eight Fiddler Crabs (on one catty corner island)
four Red Clawed Crabs (on the other catty corner island. Also, notice I cut the number in half; twice the potential size, half as many. Or I could make their beach twice as big....)
four to eight mudskippers* and
two Violet Gobies
Option 2:
1 to 2 dozen BBGs*
a few fancy guppies*
eight Fiddler Crabs
four Red Clawed Crabs and
four to eight mudskippers*
Option 3:
1 to 2 dozen BBGs*
a few fancy guppies*
eight of Fiddler Crabs *or* Red Clawed Crabs**
four to eight mudskippers* and
two Violet Gobies
Option 4:
1 to 2 dozen BBGs*
a few fancy guppies*
eight of Fiddler Crabs *or* Red Clawed Crabs**
four to eight mudskippers*
*Exact numbers subject to vary based on a lot of variables
**(Please don't make me have to pick. I love HUGE things, such as RCC [huge for a crab], but I've always wanted to witness the male Fiddler's claw in all its daily motion... :{ I can only set up one tank and my 135 is my largest.)
So? What do you think? Thanks again for everything!
<Hmm… do review earlier messages. Red Claw Crabs best kept alone. Uca species compatible with Mudskippers of similar to slightly larger size. Guppies can work with Uca and small Mudskippers. Gobioides spp not really compatible with Mudskippers, but harmless, and can get along fine with Guppies, and perhaps small crabs if the latter have land to get out onto.>
<Cheers, Neale.>

Red Claw Crab - Sesarma bidens, gen. captive husbandry... Good     10/20/12
I just wanted to write to share my experience with Red Claw Sesarma bidens crabs.

<Fire away!>
Fellow crab keepers, do not let pet stores tell you the crabs are freshwater....provide brackish water (1.005).
<For sure.>
Color will improve, molting will occur without mortality and frankly, the crabs seem more lively.
I also provide heated water to simulate tropical conditions (I live in a cold weather area).
<Wise, indeed necessary, as well.>
My tank is also set up with little coco moss "islands" and plenty of rocks, crevices, decorations to hide in.  Most important observation...THESE CRABS ARE NOT SOCIAL....I started out with five...I have one left (a male named Spiderman Crab).
<This can be a common problem, yes. Doesn't always happen -- does depend on size of vivarium, sex ratio, availability of moulting spaces. But you are quite right, as with all crabs, you should always assume they'd do better singly than in small groups.>
I have witnessed horrors only seen in movies in relation to keeping these crabs together...they will eat one another...even though my crabs are fed a variety of foods (crab pellet, fresh fruit/veggies, and white fish/shrimp), they eat one another.
<Quite so.>
I used to think it was just "opportunity to clean up" after a natural death...that is until I witnessed Spiderman Crab taking a weaker, smaller crab into his burrow (this crab had two of his tankmates--one mutilated with all legs missing and still alive--on his side of the tank and it did not take CSI to figure out what had happened - I literally caught him eating another crab's leg) of course, this crab I have left also happens to be the largest, healthiest and definitely aggressive (I put a small glass crab collectable into the tank just to see what would happen and he attacked it!)
<Nature red in tooth and claw… and as you've seen, well within the range of "normal" crab behaviour.>
Also they are curious and will definitely hide out in the filter, or even escape, so be extra careful when setting up your tank so minimize accidents.
<Another wise observation. I have kept a crab that literally burrowed through a giant sponge filter in the overflow chute down the side of a large aquarium, creating its own burrow.>
Spiderman Crab escaped via the filter and luckily my dog kept going under the chair and crying so when I investigated I rescued the crab and then redesigned the filter cords to minimize chance of another Houdini escape...recap...one crab per enclosure, brackish warm water, variety in diet, secure enclosure and add variety in decor to occupy crab = one happy crab keeper.
<Thanks for this detailed report. Do think that this will help, inform others considering these animals as pets. Amphibious crabs can be very fun "exotic" pets, particularly if you only have limited space, and their needs are minimal in terms of diet and healthcare. But there are some non-negotiable considerations you've explained here, and when people try to keep them in freshwater community tanks, or with freshwater turtles, or really anything other than a crab-specific vivarium, things can (and usually do) go catastrophically wrong. There are one or two breeding reports for this species online; if you're minded, have a read, and you might find another way to deepen your enjoyment of these unusual animals. It's not easy to do, but it is do-able. Cheers, Neale.>

Halloween Moons Crab -- mite/springtail infestation    10/8/12
Hello, I need some advice. I have two Halloween moon crabs (g. quadratus)
and I am having a problem with these little tiny jumpy white bug things that I was told could be springtails.
<Likely so. Springtails and similar primitive hexapods are common in warm, damp environments like vivaria.>
I did have living plants in the crabitat. I have isolated the crabs in a brackish water (1.005) bath and now need advice on how to sterilize the tank.
<Hydrogen peroxide is the easiest. Rinse well afterwards and it's completely safe. You can also buy aquarium sterilising chemicals from good aquarium shops.>
This is my second infestation in two months time.
<And will not be the last. Uneaten food inside the vivarium will inevitably attract more of the little hexapods, if conditions attract them. So, look at aquarium cleanliness: remove uneaten food, crab wastes as soon as possible.>
also, my one crab molted and regrew two rear legs, but now her shell is cracked and there appears to be a hole on the seam. Upon inspection the other crab has a crack along the seam as well (up alongside underneath the orange spots.
<Do make sure you're providing adequate calcium and a source of iodine. Do read:
Thanks for your help.
<Most welcome, Neale.>
re: Halloween Moons Crab -- mite/springtail infestation    10/8/12

thanks for your advice and info…
<Glad to help.>
I provide brackish water 1.005 in a one gallon jug...how much iodine should I add to the water jug...I use a table top fountain that holds @ 20 ounces at a time...but I replenish the water from the one gallon jug...the fountain has a carbon filter in next to the pump, but I still completely clean and change the water weekly.
<You can buy so-called iodine supplement for marine aquaria in some aquarium shops (it actually contains iodate/iodide salts rather than iodine itself). Dose at 50% the amount recommended for marine aquaria. Alternatively, and this could work very well with amphibious crabs, provide iodine-rich foods, Sushi Nori springs to mind, at least once a week. Cheers, Neale.>

Red Claw Crabs   1/25/12
Most people on the internet seem to think these crabs are mostly aquatic, I saw that you guys say they are mostly land.
<They will'¦>
The problem I have is that my crabs never come out of the water (I've only had them for four days, so I shouldn't say never).
<Quite so.>
I do have the tank set up as aquatic only with a few bits sticking out of the water.  But still, they seem to only like the water.  So, I guess my main question would be, why do you claim they are mostly land crabs
<Because they are -- in the wild at least. They live in mangrove forests feeding on leaf litter and carrion. Do read up on Perisesarma species, which is what these are.
They're shore crabs, If they don't come on land in your aquarium, then something is amiss. They won't come out if there's something scaring them, or if the air is too cold or too dry. They're also EXTREMELY territorial, and if one crab claims the one small bit of land, the others may not be "allowed" out.>
and is there a resource that can give me a step-by-step on how to set up and care for these crabs?
<Not that difficult. Set up something like you'd create for mudskippers, with a couple inches of warm, brackish water (SG 1.005 at 25 C/77 F is fine). An under tank heater would be ideal. The rest of the tank can be sand, rocks, bogwood. Make sure the air inside the aquarium is warm and damp, but a slight flow of air is important to prevent mould. Keep the hood secure because these animals WILL escape if they can. Use filter floss or plastic mesh to plug any large gaps. Crabs are cannibalistic at times, especially when moulting, so provide lots of caves and such hiding places.>
I am also wondering how you know so much about them, and speak with such authority when there seems to be so much miss-information out there?
<Because I'm clever. More seriously, because I'm a marine biologist by training, an aquarist by inclination, and I've spent some 20-odd years reading scientific as well as hobby literature on brackish water animals. Perisesarma spp are classic brackish water, mangrove crabs. There's really nothing at all mysterious about them. Yet unscrupulous retailers continue to sell them as "freshwater crabs" or "aquatic crabs", and willfully ignorant aquarists vigorously resist any attempt by people like me to tell them what these animals need to do well. It's significant that the people who succeed with them, e.g., actually breed them, are those who understand their ecology and provide brackish water for the adults and marine conditions for the larvae. Cheers, Neale.>

Red Clawed Crab (Pseudosesarma moeshi / Sesarma bidens), sys., fdg.   12/6/11
Thanks for the excellent and informative site. I really don't know how people managed without the web in this hobby. There is just so, so much to learn.
<Thanks for the kind words.>
I recently purchased 4 of the above for my 140L with, what I must confess, was breathtaking newbie stupidity. I thought, being from the coast as I am, a crab's a crab. It lives in the water and eats dead fish. It was in the LFS freshwater area, so I assumed freshwater.
<Ah, yes, indeed. These are brackish-water crabs.>
I now understand that they need an omnivorous diet, land and brackish water. So I went into action to see what I could do. I straightaway got two bits of bogwood stood end on in the tank and secured them above water as a temporary measure and today began construction of Island of the Crab People, Prototype 1. Layered polystyrene sewn together with fishing gut, with a small rim to hold fine gravel, on top of which I placed a few flat rocks for cover. It's elliptical and about 1 foot x 0.5 feet. This was secured to the bogwood with more gut.
<I see.>
The plans for Island of the Crab People, Prototype 2, are to include an area of the same construction and dimensions, only with a deeper rim. All layers will be aquarium siliconed together and the tray filled shallowly with gravel to make a depression for a small brackish water pond.
The finished article will hopefully be both islands incorporated in one kidney-shaped island made from sufficient layers of polystyrene siliconed together for buoyancy, but with a deeper rim than prototype 1 to hold a deeper area of sand instead of gravel, for burrowing. I was thinking of placing ballast underneath to improve the centre of gravity and the exterior will be finished by brushing all over with silicone and rolling in sand, I'll probably do a couple of coats of that.
Anyway, I thought I'd see what you thought about the remedial actions I have made/plan to make and see if you have any suggestions for improvement.
At some point in the distant future I'll set up a proper vivarium. I'm becoming attached to my Crab People already (sorry, too much South Park) and I don't mind giving them a home to themselves.
<Is usually necessary. They aren't really compatible with much else in the long term. In a really big, sandy beach type aquarium you might keep them with salt-tolerant fish like "feeder" Guppies that are fast enough to avoid trouble (fancy Guppies are too dim and too slow). But really, crabs are crabs, and best kept on their own. They're aggressive, territorial, well-armed, omnivorous, opportunistic and persistent. Not a good combination.>
In the meantime the island will have to serve as the cash isn't exactly flowing at the moment.
Now to the other questions. (It does say don't worry about length of the email in the instructions for contacting WWM - you asked for it!)
<Quite so.>
Part of what I thought about the island, except for scuttle space, was an area to place food on to stop them from dropping it in the water.
<Yes, but they will feed under water.>
From my reading and observation, I understand they like to scoff out of the water. Nope, they just drag it off the island back to a crevice in the bogwood, eat a bit and drop it in the water.
I'm assuming this is down to lack of cover on the island. Any suggestions as to what I can use, or will they make their own cover when I get sand?
i.e. burrows.
<Don't worry about it. Feed sparingly, and feed sensibly. For example, a clam on the half shell could feed several crabs. It's shell would prevent it being moved around. Likewise some soft banana smeared on a bit of bogwood would be another good food choice. When hungry, they'll scour the tank for tidbits so don't worry too much about spillage. Just remove uneaten food after an hour. A turkey baster is super-useful for spot cleaning underwater.>
I'm well briefed on what to feed them now, but how long should I leave the food around for?
<See above. Don't worry too much about this. They are scavengers, and to some degree, need time to crunch up things like the bones in whole lancefish and the shells of unshelled krill, both of which provide the calcium they need.>
With fish I give them a minute, but I can easily see that with crabs it's going to be a lot different. Also, how much food should I put down per crab and how often? I'm totally clueless about how much to feed and I can't see anything about it anywhere I've looked.
<A claw-sized hunk once a day is ample.>
I've read about adding iodine to the water during moulting. In the concentrations recommended, would this harm fish?
<Is safe. But you shouldn't be keeping them with fish anyway; at least, not fish you value. Feeder Guppies are a possible bet because they might breed quickly enough to make good any occasional problems. But even then, any Guppies that move slowly or get old will be eaten -- and not everyone enjoys the sight of a still-breathing, still-living fish being dismembered by a crab. Trust me, these crabs can be brutal.>
I have come across suggestions that the amount of salt that the crabs require wouldn't even harm a salt intolerant fish, i.e. salt to SG 1.010.
I'm taking this with a pinch of, um, salt(!). Could you confirm yay or nay on that?
<SG 1.010 at 25 C/77 F is about half-strength seawater. That's ideal, but not essential. SG 1.005 is a good starting point and will cost half as much!>
The other thing is they don't seem to be actually using the island I have made. One has come over, dragged a bit of lettuce back to the bog wood, chomped for a while and dropped it in the water. It then returned, hauled away a bit of salmon (better fed than the cats, these things!) and ate a bit before, yep, it dropped it in the water. Again I think this is maybe due to lack of cover or it could just be early days yet and exploration will occur overnight.
<It is their nature to drag, dismember, and generally make a mess. Don't worry too much.>
Any comments you can make would be appreciated, especially on feeding.
<Best wishes, Neale.>
Re: Red Clawed Crab (Pseudosesarma moeshi / Sesarma bidens)   12/8/11

Hi Neale
Thanks for the advice. I really appreciate you taking the time to help me out. Unfortunately I am going to pickle your head just a little further.
A vivarium with feeder guppies sounds ideal, really. I'm not bothered if the crabs catch the occasional fish but I would object if the guppies had no chance, though.
<Quite so. A lot depends on the size of the tank. If there's only 5 or 6 gallons of water, and it's all just a couple inches deep, then the odds aren't in the favour of the Guppies. But if the vivarium is a 55-gallon tank and there's 6-8 inches of water, so some 20 gallons of the stuff, then the Guppies might be okay. Use some common sense. Basically, if the crabs can catch small fish, they will. Fiddler Crabs tend to be quite safe with fish, but Red Claw Crabs are much more vicious.>
It would be great to see the crabs with damp sand to burrow in and being able to behave a bit more normally than just sulking on a bit of bogwood.
<Yes. Leaf litter, moss or coir (coconut fibre, sold in reptile pet shops) can work for this.>
I've had cats all my life so a bit of predatory brutality isn't exactly unusual for me. Still, "aggressive, territorial, well-armed, omnivorous, opportunistic and persistent" makes it sound like this is going to be a real adventure!
<Ah yes, crabs and cats share very much the same outlook in life, dividing everything into [a] stuff I can kill and [b] stuff I can't kill.>
My only one worry with feeder guppies is WWM's warning to usually steer well clear of them due to ethics and disease.
<Quite so, in terms of using them as live food. This is much different. Where sold, "feeder" Guppies are crossbreed Guppies, and genetically they're much better than fancy Guppies. They're also cheap. So you can try a few out and see what happens.>
I won't be putting the guppies at the mercy of a dedicated killing machine that's much bigger than them, so ethics doesn't really worry me. As long as they are generally able to avoid the crabs that's fine, since it's more or less the way things go in nature. Disease is, however, more of a worry. Are fish likely to pass pathogens/parasites over to inverts or are they too far removed?
<Little to no risk. Crabs are scavengers anyway, so they're pretty resistant to disease right out of the box. They feed primarily on dead and sick animals rather than healthy ones.>
From looking at these little guy's natural habitat, mangrove leaf seems to be their staple diet in the wild. Apparently oak leaf is a suitable substitute but I can't honestly remember where I found that. I've been digging deep on them and read so much that it's becoming a bit of a blur.
<You can actually buy live mangrove plants, though they're mostly sold to marine aquarists.>
It's hard to find any proper scientific literature on them though, sadly. I confirmed the leaf diet with someone's PhD thesis and that's about as good as it's got. From the same thesis, silt would appear to be the natural substrate at the sites that were investigated, i.e. very fine particles, and that stands up for an estuarine environment. Do you or any others have any experience of using silt in aquaria? My first thoughts are anoxia in the sediment and difficulty in keeping plants to break it up owing to the crabs munching them.
<It's doable, but not ideal. For one thing, silty water is murky water, which isn't attractive. A mix of 50/50 silica sand and coral sand will give you an attractive substrate with some buffering capacity, and you can stir in some crushed shells to add interest. Clam shells and mussel shells would both be very authentic. You can also use silicone to glue together "reefs" of oyster shells, either as lumps by themselves or onto fake mangrove roots -- either would be extremely authentic additions to any brackish water system.>
As a related aside, is it possible to get hold of tropical invertebrates other than shrimp, crabs, crayfish and snails.? i.e. worms and other substrate dwellers. Obviously anything that hatches into an adult with wings is out. I'd be barred from stocking anything if a swarm occurred in the living room.
<There are such animals to keep, but selecting them is difficult. But if you know where to look, or can order them, yes, they're out there. There are lots of brackish water Nerite snails, e.g., Clithon species. though crabs will probably eat them. There are brackish water hermit crabs as well, including Clibanarius tricolor, the popular Blue-Legged Hermit kept by most reef tank keepers. It needs high salinity, SG 1.010 upwards, but is cheap and hardy. Again, wouldn't trust this completely with the Red Claws. Then there's the Mangrove Horseshoe Crab, Carcinoscorpius rotundicauda, a species sometimes sold as a freshwater species but like the Red Claw really needing middling to high salinities in the long term.>
Another concern I have with the crabs is that my tank pH is at 6.8, which I know is a little low for them but, as I understand it, brackish will be >7.5 and within their suggested pH range.
If I set up a pool on their island as brackish will they end up suffering pH shock if they are chopping and changing between pool and tank? Or do crabs, being "amphibious", not work that way? If it is an issue, I may be able to persuade wifey-o that a vivarium is essential and is needed soon.
<Just change the water completely. The crabs walk in and out of different puddles in the wild, and really aren't affected by pH, salinity or hardness in the same way as animals that are completely submerged all the time.>
I doubt that they're going to be a real danger to the fish I'm keeping them with now - 1 lonesome blue gourami. I might actually need some help on this little terror too. When the crabs get bigger it might be more of a worry. They're only at 0.75" to 1" carapace width just now.
Would salt to SG 1.005 harm the gourami?
I've read most anabantids are extremely salt intolerant.
<Yes, with very few exceptions, e.g., Anabas testuideus, the Climbing Perch, which is actually quite common in low-end brackish water environments. There's also -- amazingly enough -- a brackish water Betta species, called Betta sp. "Mahachai".>
1.005 doesn't sound like much but it's about 10 000ppm as sodium chloride (not that I'll be using sodium chloride, don't worry).
<Indeed, it's about 9 grammes marine aquarium salt per litre, well above what freshwater fish enjoy. Some can tolerate this, to be sure, but it isn't ideal.>
And the gourami'¦
The gourami bullied her other gourami tankmate, I didn't think much of it, it wasn't too serious. Then the tankmate died. No fault of the bigger gourami, just the fishkeepers who thought that a filter from an already cycled tank meant that the tank we put the filter in was ready to go. We slapped our foreheads, let it cycle and got a couple of Bolivian rams to add. The surviving gourami hounded them to death. The poor little things didn't stand a chance, stressed with the transfer they were gasping a bit, and listless.
<Oh dear oh dear. I have to admit, I'm not a fan of Three-Spot Gouramis in either their Blue or Golden form. One of the first fish I kept, harassed everything in the tank, and haven't touched them since.>
I saw this behavior with newly introduced golden rams before, so I wasn't unduly concerned, but the gourami moved in and started fin-nipping and not giving the rams a chance to stay still and get over the stress. Both were dead the next day. Could it be the gourami now sees the tank as "her's"?
Would adding more gouramis help disperse the aggression amongst the same species?
<Can, yes, but assuming you add so many she can't bully them all, i.e., six or ten of them. Actually, this species does rather well in large groups.>
Would adding some Danios to distract the gourami work?
(Is this what a dither fish is?)
<No. Dither fish convey to bottom-dwelling fish (such as cichlids) that it's safe to come out. The theory is that bottom dwellers can't see above the waterline, so don't know if there's a predator there like a heron or fisherman. But surface-swimmers do, because they're swimming up close. So, if the Danios are nervous and hiding, then the bottom-dwellers will assume there's a danger. If the Danios are happy, the bottom-dwellers will come out of their hiding places.>
I'd like to see her try to nip a Danio! We're also considering that she might just be an evil little sod in character, but we don't really know.
<Could easily be a bad tempered one, yes. Some Three-Spots are lovely, others mean.>
There seems to be a lot of conflicting opinions out there on the net. Admittedly it's been my wife that's been doing most of the research on this front so I'm not fully up to speed. Some are saying gouramis are fairly aggressive and should be kept singly, some to keep them as a school of four, others that the school of four should be different varieties. I trust the judgment of you folks on WWM more than most so a bit of help would be welcome.
<Just isn't a reliable species, but does tend to harass "similar" fish like other Gouramis as well as Cichlids, while generally ignoring dissimilar schooling fish like tetras and barbs and Danios.>
<Cheers, Neale.>
Re: Red Clawed Crab (Pseudosesarma moeshi / Sesarma bidens)  12/9/11

Hi Neale
Don't worry, I'd give the fish in a vivarium plenty room to move.
Thank you for advice on substrate - I really hadn't thought about the display aspects of a silt based vivarium. As for invertebrates, I'll have a look about.
Cheers for the heads up on the brackish Betta. I love anabantids and having seen some pics of Mahachai I think they top splendens in beauty by a long shot. One for the future I think. Do they have a similar character to splendens? e.g. males in a separate tank etc.
<Yes, Mahachai seem very similar to wild-caught Betta splendens. They do well in captivity, but sadly, they're not much traded.>
"Ah yes, crabs and cats share very much the same outlook in life, dividing everything into [a] stuff I can kill and [b] stuff I can't kill" - this cracked me up! I can see my little crabby killing machines and I are going to get on just fine. If the furry killing machines don't get them first, that is.
<Quite so.>
The gourami I really don't know what to do with. I had read about them before she was introduced but I never read about them being evil little sods. We were hoping to make Ctenopoma (spotted climbing perch) the focus of the tank but I fully believe she'd kill one of those. (Obviously crabs and slow-moving Ctenopoma wouldn't be mixed).
<Ctenopoma acutirostre are some of my favourite fish, but yes, they're slow, stealthy fish with very mellow personalities, and shouldn't be kept with anything aggressive. Corydoras, Congo Tetras, that sort of thing make good companions.>
We might have to look at rehoming Madam Gourami. Any suggestions on this front? I've read a lot of American sites that seem to say you can take fish to LFS and they'll take them. Is this the viable in the UK or is it a case of an advert at pets at home?
<The Maidenhead Aquatics chain will normally take unwanted fish and rehome them. Check their web site for a branch near you.>
If you've any experience of keeping Ctenopoma words of wisdom would also be gratefully received. I know - gill spines, BIG mouth, shy and slow to eat but that's all from web pages. If you have any pointers from direct experience I'd love to hear them.
<There are some nice articles here at WWM:
I have kept them, and they're very hardy and easy to keep, except in one regard: they usually don't care for flake or pellets, so you'll need wet-frozen bloodworms, chunks of fish and seafood, earthworms, and so on.
In terms of personality, I find them extremely similar to Angelfish, except with somewhat larger mouths, so tankmates need to be somewhat larger.
Once again, thanks for taking the time out to help this pair of well meaning but inexperienced newbies
Gordon and Denise

Scylla serrata? BR crab ID, care... 12/4/11
Today while checking in at the local Vietnamese market (I'm always amazed at the things that turn up there in the seafood sections. I've picked up some pretty neat aquarium inhabitants there), I noticed they had something labeled "freshwater crab" and seemed to be active and doing well in room temperature water. I picked one of them up, as I've always wanted some large crab species that didn't need a chiller. At least, hopefully these don't need chillers.
<Quite so. Scylla serrata is a tropical species. It's also frequently used in laboratories where it has proven to be quite a hardy animal. One of my professors at university had done some neurobiology work on this species.>
After a bit of research, I'm fairly sure she is a 2 pound female Scylla serrata. As of now, she is sitting in a 40 gallon by herself until I get a good idea as to what sort of setup she needs. My main problem is, I have found little to no information on keeping these in captivity. Apparently they are brackish?
<In the general sense, yes. They move in and out of estuaries, and seem to be tolerant of a wide range of salinities, at least as adults. The larvae are less tolerant, but that's only an issue if you're planning on breeding from her!>
She is in full fresh now, and I'd like to get her in brackish as soon as possible if it'll be healthier, but I'm not really sure what salinity to go for.
<Something from the middle of the range upwards would be ideal, from about SG 1.010 at 25 C/77 F upwards. If you have a saltwater tank already, then adding one bucket of marine aquarium water alongside every one bucket of tap water should be an economical way of maintaining this animal. She'll certainly be much more tolerant of nitrate than, say, corals. Of course you could also keep her in marine conditions.>
What tank size should I put her in?
<Big as possible.>
I have no idea how much waste a crab this size is going to make.
<A lot! On her own, I'd have though something around the 55 gallon mark would be the minimum, given she's already a big animal. A heavy-duty external canister would be required for filtration -- or at least something with a high turnover and that you can clean easily and regularly.>
My other question is diet. What would be the best thing to entice her to start eating?
<Like virtually all swimming crabs, Scylla serrata is a predator. A good starting mix would be frozen lancefish, cockles, and, in modest amounts, mussels and unshelled shrimps (these contain a lot of Thiaminase, which you probably want to minimise). As with any large crab, iodine is going to be a key nutrient, as well as calcium, so an iodine supplement, at 50% dosage, as used for reef tanks will be important.>
She's active and aggressive, which I take to be a good sign, but shows no interest in food. I'm hoping she'll come around and eat later and is just stressed out now or something.
<Agreed. Plus, at very low salinities, she may well be "unhappy" in whatever sense that means to a crab.>
I attached a picture in case you have any other ideas to what species she is. (Disregard the crab straightjacket, they all had those on at the market, and I took it off as soon as we got home.)
<Cool looking best.>
Thanks for any help.
<Best of luck, Neale.>

Salt, plants, and crabs -- 07/21/11
Dear plant and crab expert,
<Yikes! Quite a combo, there'¦>
I'm converting one of my 10 gallon tanks to a paludarium. Most of the tank will be water (approximately 4 gallons), with lots of shelves on the back (for plants), and a shelf on the left with a ramp for easy access in case a land animal falls in the water.
<I see.>
I'm planting it with hairgrass, several crypts, and any other plants I can think of, even though I want it to be an Asian biotope (Samolus sp, baby tears, etc). I'd like to host red claw crabs (Perisesarma bidens),
<These are best kept as brackish water animals
and don't do well in freshwater indefinitely.>
Hermit crabs (Uca sp.),
<These are 100% brackish/marine animals -- whatever the retailer says -- and will die unless kept in brackish to marine conditions.>
and some aquatic insects (springtails, water louse, water striders).
<May not/will not be compatible with brackish water livestock.>
I can't really find a solid answer about how much salt is needed'¦ I was hoping 1 tsp of reef salt per gallon would be enough.
<SG 1.003 would be the absolute minimum; that's about 6 grammes per litre of water. Teaspoon measurements are very, VERY inaccurate, but 6 grammes is about 1 level teaspoon. Check it yourself using kitchen scales and act accordingly. Above SG 1.003 you'll have problems with plants; below, the Uca and probably the Perisesarma will be less robust, dying.>
I also can't really find out whether that would kill the plants or not.
<May well do unless you choose plants carefully. As it happens, Samolus valerandi is extremely salt tolerant. On the other hand, Hemianthus callitrichoides is not. Eleocharis species sometimes tolerate slightly brackish water but it varies between species. Hardy Cryptocoryne species like C. wendtii tolerate slightly brackish water, and C. ciliata is a true brackish water specialist. So do your research here, for example:
If I use reef salt, would I still need iodine supplements?
I'll also likely add some glass shrimp to the tank- if they get eaten, that's okay.
<These tolerate slightly brackish water well.>
Because the land area is built of shelves, is it ok if the crabs don't have a dry area to tunnel in? The terrestrial and aquatic plants should provide hiding places to help them feel secure.
<The plants will also be food for the crabs, especially the Perisesarma.>
Can you recommend any other inverts that would do well in this setup?
<Crabs generally don't cohabit with anything, and you would be very unwise to mix Perisesarma and Uca; the Uca are essentially non-aggressive (if territorial) deposit feeders that sift mud and algae, while the Perisesarma are aggressive opportunists that will view the Uca as potential food.>
I was also considering Nerite snails'¦
<Can work extremely well with Uca and shrimps.>
Thanks, David
<Cheers, Neale.>
Re: Salt, plants, and crabs -- 07/21/11
What about moon/Halloween crabs?
<Gecarcinus quadratus.>
I was thinking maybe mixing a mostly terrestrial crab with a mostly aquatic crab so the smaller ones could escape'¦
<Not a chance of mixing Gecarcinus quadratus with Uca spp.; do understand that crab species DO NOT cohabit in the wild, and most view one another as either rivals for living space or potential meals. There is an ample literature on this based on crabs in reef tanks; do read.>
It's ironic to me that Uca might be less likely to eat plants, but prefer more salt'¦
<Hmm'¦ not really ironic, merely a reflection of the fact these crabs come from beaches and salt marshes where freshwater aquarium plant species are absent.>
I might have to decide whether to kill my plants with salt or serve the crabs a salad bar. It's a shame. I might end up having to scrap the crabs altogether,
<Do look at Thai Micro Crabs.>
and go with Cambarellus Patzcuarensis var. Orange, also known as the dwarf mexican crawfish.
<A fine beastie, though irregularly traded.>
At least it's plant-safe and peaceful according to everything I've read.
<Hmm'¦ the smaller crayfish are less aggressive and less destructive, but it would be unwise to assume non-aggressive and non-destructive. Potentially safe in mixed species tanks, but do bear in mind these have only been in the trade a year or two, so there's very little experience to draw on, and certainly not every combination of crayfish, fish, and plant hasn't been tried.>
Not sure if it would ever leave the water though..
<Fully aquatic.>
I don't want the land area to go to waste.
<Paludarium systems tend to work best with frogs, to be honest, rather than inverts. You might consider tree frogs alongside, say, similar sized aquatic frogs or newts. Mudskippers are of course another possibility, and can, if species are chosen carefully, cohabit with Uca spp. and certain brackish water livebearers, such as Mollies. Provided the plants above the waterline are insulated from the brackish water and watered with freshwater, there's little risk of salt poisoning them, and conversely, there are true brackish water plants that might be placed under the waterline to green things up there. Cheers, Neale.>
Re: Salt, plants, and crabs 7/23/11

Sorry, I've been doing a lot of research. I think instead of giving the fiddler crabs (Uca sp) the minimum amount of salt, I'll give them whatever is ideal. Do you think 1.008-1.010 would be about right?
After a lot of research, I've found a list of plants that should survive at those levels... I'll put it here so you can share it with others. I assume some of these plants won't make it, but most should, as long as they're
acclimatized slowly.
Variegated Acorus (Acorus gramineus var. 'variegatus') Terrestrial/Emersed
Cryptocoryne pontederiifolia Terrestrial/Emersed
Crinum Calamistratum Submerged
Lilaeopsis novae-zealandiae (Microsword) Terrestrial/Emersed
Glossostigma Terrestrial/Emersed
Java Moss Terrestrial/Emersed
Java Fern 'Windelov' Undecided
Anubias Nana Emersed
Azolla Floating
Various Crypt species (already had) Submerged, will allow to grow emersed
Hairgrass Submerged
<Would be very, VERY surprised if most/any of these would survive above SG 1.005 at 25 C/77 F. Would strongly recommend you run the tank at SG 1.003 at 25 C/77 F to start with, using those plants. That's just short of 20% seawater, and more than ample for most brackish water fishes and livestock.
It'd be acceptable for your Fiddler Crabs, and being relatively benign animals, you'd have lots of options for things like Endler Guppies, Black Mollies, or, if you can get them, oddball livebearers such as Micropoecilia parae melanzona, Micropoecilia picta, and Limia nigrofasciata.>
For livestock, I'm thinking (I know, I can't seem to make up my mind!) 3-5 Fiddlers, 5-10 opae'ula shrimp AKA Halocaridina rubra (I'll have hiding places to let them get away from the fiddlers in case they think they're food)
<Very likely. Do bear in mind Cherry Shrimps adapt well to slightly brackish water, and in fact virtually all shrimps are worth trying at low-end brackish water.>
In addition, Fiddlers are mostly Diurnal, while the Opae'ula shrimp are mostly nocturnal. To wrap it up, I think I'll throw in a couple horned/corona Nerites and a ghost shrimp.
<Clithon corona, Clithon sowerbyana and Neripteron auriculata would all thrive in brackish water.>
The tank is a 10 gallon. I know they like to dig, but I think they'll have to settle for man-made tunnels made out of 1/2" PVC pipe.
<Cheers, Neale.>

Crab identification 11/17/10
Hello, I was wondering if you could help me identify a large crab that I recently bought from Petco. They had it labeled as a "Thai Red Devil Crab" but all my internet searching on this name has not found any results. He is about 4 1/2 to 5 inches across with a purplish red shell. His left claw is much bigger than his right, but not quite as much of a difference in claw size as Fiddler crabs. On a side note, I was wondering if crabs use their large claw for anything other than attracting the ladies. Anyways, I currently have him in a 10-gallon semi brackish tank (he will be upgraded to a 25 soon) with a cave to hid in and one of those small turtle docks to allow him to get out of the water. Is this setup ok or should I switch to a terrarium? I also included some pictures of him and one of my crayfish for your convenience. Any help would be appreciated.
<Hello Zach. You appear to have a male "Thai Devil Crab". They're periodically traded but I have no idea what their Latin name might be. In any case, they get quite large, and they are notoriously aggressive and predatory. They do appear to be more or less aquatic in the same way as many other estuarine crab species -- i.e., by choice they stay underwater, but that can venture onto land for short periods. An arrangement of rocks above the waterline that allowed the crab to bask under the light should it choose to would be helpful, but otherwise don't worry about providing this beast with a land area. Thai Devil Crabs don't seem to be amphibious in the same way as Soapdish Crabs or Red-Claw Crabs. One clue is their rather flat body compared to the much more boxy, deeper body shape typical of amphibious and land crabs. They do require brackish conditions though, SG 1.005 is ideal, and I'd also recommend using marine aquarium Iodine supplement at about 50% the recommend dosage. Although crabs are carnivorous given the chance, their diet should be distinctly mixed with plenty of green foods alongside meaty treats such as tilapia fillet and unshelled prawns. As for differences in the size of the claws, so far as I know this species has claws of similar size, so your chap has probably lost a claw at some point, and it'll be a few moults until the new claw matches the other claw in size. Crabs do indeed use their claws for all sorts of things, from signaling to one another through to dismembering prey, snipping off vegetation, crushing snail shells, climbing up things, and of course for nipping at anything that attacks them. Crabs are fascinating animals, among the Nature's success stories, and quite a sophisticated and modern group of animals despite their sometimes archaic appearance. Cheers, Neale.>

Re: Crab identification, salt 11/17/10
Hello again and thank you for the quick reply. I don't think my crab lost his claw in a fight as all the other crabs in the tank also had one large and one small claw. He also uses his small claw to pick up food like
fiddler crabs. His large claw has roughly the same proportions to his body as a fiddler but his small claw is a little bigger proportionately. If both his claws were the same size as his left I don't think he could move them. I'm sorry if you didn't get the picture I will paste it to this message. As for the salinity, should I use marine salt or is their a salt specifically made for brackish water? Sorry if that sounds dumb I don't know much about saltwater tanks.
Thanks in advance
<Hi Zach. The claw could easily have been damaged prior to collection.
While it is not uncommon for crabs to have dissimilar sized claws through accidents and fights, Fiddler crabs are exceptional in having one claw massively overdeveloped as a signaling/fighting tool rather than one for feeding and climbing. So far as I know, crabs don't do the lobster thing of having one claw for crushing and one claw for snipping. Yes: marine salt mix is what you need, not "tonic" or "aquarium" salt used for treating freshwater fish. Around nine grammes per litre should be ample, with iodine added. Without the iodine, large crustaceans are extremely prone to moulting problems in captivity. Iodine-rich foods such as Sushi Nori make particularly good supplements to their diet for the same reason. Cheers,
Re: Crab identification, sys 11/17/10
Hi sorry for so many questions (this is the last one) but how long can these crabs live in freshwater? The salt in his tank is "aquarium" salt. I might not be able to get marine salt for a couple days will he be ok until then? I don't know how long Petco had them in freshwater but he's been in my tank 5 days. Thanks.
<Hello Zach. "Aquarium" salt will do for a few weeks, but in the longer term the lack of calcium salts as well as iodine could cause problems. If you can, add 1 teaspoon baking soda (sodium bicarbonate) and 1 tablespoon Epsom salt (magnesium sulfate) per 10 litres alongside the aquarium salt.
These will provide some of the minerals crustaceans need for their shells.
Also, add the iodine, either in the water, or through foods rich in iodine (there are some special crab pellets available from companies like JBL).
Cheers, Neale.>

Can a crab heal damage to its eye?... and another question. Callinectes spp. habitat, comp. 8/8/09
Hello WetWebMedia crew! A few weeks ago I received a medium sized Cardisoma guanhumi in the mail. His body (without the legs) is probably about 5 inches across and he's a lovely blue color. My only concern is that I noticed a strange brown spot on his left eye. It is the same color as the coconut fiber substrate that I have been using, so at first I was not alarmed. However, it has been a long time now and that spot is still there in the exact same spot and I have never seen him make any attempt to wipe it off. Upon further inspection the spot has a different texture than his surrounding substrate and looks like his eye is actually damaged (BTW his eyes are yellow). I do know that crabs can regenerate lost limbs, and I also know that crabs have compound eyes like that of a fly or a wasp. My question is this: Can a crab regenerate from eye damage with successive molts, or is an issue like this permanent?
<Not the eye itself, no... just the exoskeleton... Perhaps this mark is superficial, just on the external non-living matrix, and will be shed...>
My picture of the crab is over 2MB in size, far larger than what you guys said you'd like to deal with. Instead I'll post a link to a website where I asked this same question (its always good to get a second opinion.)
<... this does look like something "outside" to me... and the left eye still functional underneath>
Second Question:. The person who I bought this lovely animal from is also offering Blunt-Tooth Swimming Crabs (Callinectes bocourti). He labels them as "Barbados Freshwater Crabs". They certainly look like lovely animals. He did state to me that they'd be much happier in brackish water and that freshwater should only be a short-term arrangement for them.
<I agree... is really a marine animal>
First of all, can these animals survive in the long term in a freshwater habitat?
In spite of what he told me, I have heard of Blue Crabs (Callinectes sapidus) being kept indefinitely in fresh water and I don't find it unlikely that this closely related species can't do the same.
<A reasonable assumption... though I don't think/consider that either do "ideally" in totally freshwater settings indefinitely. For instance, I doubt that they will moult, grow t/here>
Also, in my 20 gallon tank I have a blue crayfish and a LOT of baby ghost shrimp (who's population exploded after the crayfish failed to eat the original 3 I put in there). Is there any chance that the crab and the Cray can forge a peaceful (if tedious) co-existence or is there really no hope for a good outcome if the two were to meet?
<Not likely to "get along" IMO/E>
Thank you VERY MUCH for your time.
<Welcome. Bob Fenner>

Crab from Wal-Mart... NO! 12/12/08 I just bought a crab from Wal-Mart and it was labeled Red Thai Crab. <Perisesarma bidens, I'd imagine. A small (5 cm) potentially predatory brackish water crab. Doesn't do well in freshwater (i.e., it dies) and needs mostly land with just a little water for bathing.> <<Dang! I thought, had heard/read that WM was getting out of the livestock biz... Now this!? RMF>> I read on here that a Fiddler Crab has one large claw and one small. <Uca sp; only the males have a giant claw, the females have equal claws.> My crab is just like this and I was wondering if Red Thai Crabs are the same way. Also I need to know how to care for it. <Basically you need a vivarium, similar to what tropical frogs need, except the water half of the tank should have around 6-9 grammes of marine salt mix per litre of water. So, get a 10 or 20 gallon tank. Fill with rocks, coral sand and bogwood to create mostly land. Fill with a couple of inches of brackish water. Use a heater to keep it at 25 C/77 F. Make sure there's a tight fitting hood: these crabs WILL escape given even half a percent of a chance!> I have hermit crab food that Petland told me they would eat. <Eat most anything. A bit of fish flake, the odd piece of white fish or seafood, and regular servings of vegetables such as tinned peas and sliced cucumber.> Do I have to supply heat for it or will it be fine in it's pet carrier with just the heat from the house? <Needs heat. Will die at room temperature.> In it's carrier it has aquarium gravel and a half coconut shell and enough water to come up to the top of the gravel but I made sure to put more rocks on the one side of the carrier so he would be out of the water when he wants? <Too small.> Can they drown if I have to much water? <Yes; it's a LAND CRAB. It uses water for breeding and drinking, but that's about it.> Oh and about his size he is about one inch in total size (legs and all). I understand I haven't given you much to go on but I don't have the right equipment to send you a picture. Any help you can offer would be great. Thanks. <Good luck, Neale.> <<I apologize to Neale for writing over his response, but PLEASE, DON'T buy these animals... write to Wal-Mart... protest they're offering of inappropriate life to consumers... Boycott their purchase! Bob Fenner>>

my crab... F, really BW... color change... beh. -- 06/12/09
Dear Crew;
I have a red clawed crab that I have had for almost 6 months now. He always seems pretty happy and forages around a lot for food. I feed him shrimp pellets and the odd tiny piece of orange (which he attacks and drags into his cave to devour). Today I looked at him and he has suddenly gone really red. I mean really red: his legs, his chest, and even some of his back. The little guy has molted twice now and I don't remember the colour change. He seems really active, the water is clean, I don't know if something is
really wrong, or really right. Can you help me?
<Hi Rachel. It's difficult to know whether or not what you're seeing is normal, and the best approach with crustaceans generally is to focus on preventative healthcare. We know precisely what Perisesarma bidens needs to do well: an aquarium with dry land to explore; marine aquarium iodine added at half the normal dose; and brackish rather than freshwater conditions, 6 to 9 grammes of marine salt mix per litre of water being adequate. If you do all these things, your crab should be in good health. If you're not doing all of these things, then it's possible you're seeing some sort of negative reaction. If he's active, that's a good sign, so if you correct conditions in the tank, hopefully he'll settle down and have a healthy life. Cheers, Neale.>

Crab from Wal-Mart... NO! 12/12/08 I just bought a crab from Wal-Mart and it was labeled Red Thai Crab. <Perisesarma bidens, I'd imagine. A small (5 cm) potentially predatory brackish water crab. Doesn't do well in freshwater (i.e., it dies) and needs mostly land with just a little water for bathing.> <<Dang! I thought, had heard/read that WM was getting out of the livestock biz... Now this!? RMF>> I read on here that a Fiddler Crab has one large claw and one small. <Uca sp; only the males have a giant claw, the females have equal claws.> My crab is just like this and I was wondering if Red Thai Crabs are the same way. Also I need to know how to care for it. <Basically you need a vivarium, similar to what tropical frogs need, except the water half of the tank should have around 6-9 grammes of marine salt mix per litre of water. So, get a 10 or 20 gallon tank. Fill with rocks, coral sand and bogwood to create mostly land. Fill with a couple of inches of brackish water. Use a heater to keep it at 25 C/77 F. Make sure there's a tight fitting hood: these crabs WILL escape given even half a percent of a chance!> I have hermit crab food that Petland told me they would eat. <Eat most anything. A bit of fish flake, the odd piece of white fish or seafood, and regular servings of vegetables such as tinned peas and sliced cucumber.> Do I have to supply heat for it or will it be fine in it's pet carrier with just the heat from the house? <Needs heat. Will die at room temperature.> In it's carrier it has aquarium gravel and a half coconut shell and enough water to come up to the top of the gravel but I made sure to put more rocks on the one side of the carrier so he would be out of the water when he wants? <Too small.> Can they drown if I have too much water? <Yes; it's a LAND CRAB. It uses water for breeding and drinking, but that's about it.> Oh and about his size he is about one inch in total size (legs and all). I understand I haven't given you much to go on but I don't have the right equipment to send you a picture. Any help you can offer would be great. Thanks. <Good luck, Neale.> <<I apologize to Neale for writing over his response, but PLEASE, DON'T buy these animals... write to Wal-Mart... protest they're offering of inappropriate life to consumers... Boycott their purchase! Bob Fenner>>

Fiddler crabs versus peacock eel 10/21/08 Hi <Hello,> I have a freshwater tank with three gold fiddler crabs, one male and two female. <Uca spp. are brackish water animals... don't last long in freshwater conditions... On the plus side, at least some Spiny Eels tolerate brackish water well, and may even be healthier in it than freshwater.> Well I got a peacock spiny eel, who was about 5 inches, and the next morning he was being eaten by the female crabs. <The eel died; the crabs ate the corpse. Spiny Eels die very easily, frequently from bacterial infections. For example, they can't be kept in tanks with gravel. Must be sand. Gravel scratches the skin, allows bacteria to get past the mucous layer, and within days they die. This happens SO OFTEN that it is depressing. Brackish water around SG 1.003 (as opposed to "teaspoon tonic salt per gallon" nonsense) may be beneficial to Spiny Eels because it minimises the risk of bacterial infections.> I don't understand what happened. He was perfectly fine all day long... and I know that my tank is in great condition. <Do you have sand or gravel in the tank? If gravel, that's likely part of the issue. Spiny Eels are also easily starved. You can't keep them with things like loaches and catfish because they don't compete for food. If you stick one in a community with loaches and catfish, it will get steadily weaker with time. They obviously don't eat flake or pellets, and need a meaty diet of things like earthworms or frozen (not freeze dried) bloodworms. Just getting food into them is hard enough without keeping them with other nocturnal fish that steal the food first.> Is it possible that the crabs could have killed the eel? <No. Uca spp. are primarily detritivores, though they will eat carrion.> The eel was somewhat slow moving and was still very young. I am very upset about the eel, it was very beautiful and I would really enjoy having an eel in my community tank. <Sadly, these aren't "easy fish" and I'd encourage you to read my thoughts here before doing anything else: http://www.wetwebmedia.com/FWSubWebIndex/spinyeelsmonk.htm > Ashley <Cheers, Neale.>
Re: fiddler crabs versus peacock eel 10/21/08
Thank you so much for the fast response! <Most welcome.> Well I do have a sand/gravel substrate, however the aquarium store had large gravel. <Hmm... in my opinion, plain smooth silica sand is the way to go, particularly with small (sub-20 cm) specimens.> And the eel was buried in there when I got it. Do you think it is possible that the eel got the infection at the store? <Quite possible.> I watched the eel quite intently and he never buried himself. <Possibly prefers the hiding places available above the substrate. In any case, they feed by pushing the rostrum (the "trunk" on the nose) into the sand to uproot insect larvae and worms. So even at that level, sand helps.> He actually spent most of his time swimming near the top of the water. <They do indeed like swimming among the roots of floating plants. They're great escape artists though, so be warned that they're also apt to jump out, if they can.> Also do you have any suggestions on what I could do to get my tank better prepared for a peacock eel? <Do read my article; that's everything I know about them!> I have three small Cory cats, will they be a problem for the eel? <Does rather depend on the size of the tank and how much food you put in. Assuming you were generous with the food, these fish might get along just fine. The real problems come with "bullies" like loaches and Plecs that will keep the Spiny Eel away from its dinner. Earthworms are the secret to success with the Mastacembelidae, and they will thrive on these tasty morsels.> I guess I should let you know that I have a 55 gallon tank with a mostly sand substrate. There is some small white gravel mixed in with the sand. <Hmm...> I have got platies, swords, mollies, tiger barbs, 2 rainbow fish, paradise fish, the Cory cats, and the crabs. Everybody lives perfectly fine together. I usually put a small amount of aquarium salt in the water. Would this be recommended for an eel? <I suspect the Fiddlers are on borrowed time. They're amphibious and will spend all their time trying to get out. The vast majority of specimens in freshwater aquaria last but a few months. It's a shame they're sold at all, to be honest. Adding "small amounts of salt" won't really have much effect either way. They won't make any of these animals healthier, but if you want to waste your money on boxes of salt, then go ahead, you aren't doing any harm either.> Ashley <Cheers, Neale.>
Re: fiddler crabs versus peacock eel 10/21/08
Well thanks again...I know the crabs need air every now and then. <No, it's not "air now and again" for these crabs. They're land crabs. They live, feed, socialize on land. They only go into the water to moisten their gills and to breed. That's it. Otherwise they're as much land animals as, say, frogs. When kept properly they spend 95% of the time on land. The males are very cute, standing about waving their giant claws to scare rivals and flirt with females. This is why they're always trying to escape: it's like trying to stop a bird from flying away.> I have an external power filter and the crabs climb up the tubes. But i have built a plastic mesh enclosure so that the crabs can get to the air but not fully escape. <Sooner or later, crabs escape. I say this as someone who had to get his parents to take apart their kitchen units to rescue a Cardisoma crab when I was a teenager! The thing was the size of a softball and yet managed to escape...> I read your article and it definitely gave a lot more knowledge about the eels. I do believe that if I try eels again I will get the gravel out and get some live worms... You've been most helpful! Ashley <Happy to help. Enjoy your fish. Cheers, Neale.>

Re: Crab Questions, Fiddlers fiddling about 10/16/08 Good evening, As an update of sorts, the day after this email I had a problem in the Fiddler Crab tank. The reservoir previously described had served me well for maybe a few months or so, but for some reason it backed up and flooded/washed out some of the land portion. I had to do some temporary rearranging in the tank and remove the circulating pump and also put in a different filter that wouldn't suck up the sand until I could do another setup. The next morning I was surprised to see the smaller female (who had been missing a leg from the beginning, now carrying eggs) with two more legs missing. <Mmmm> I immediately spotted the legs lying near the food dish and observed the male (about the same size) chasing her and trying to grasp at her. I had never seen him act like this before. I reached down to scare him away from her and within 30 seconds he was chasing her again. <As a food item> I decided to go ahead and put her into the hatching tank that I had set up (ridiculously small at two and a half gallons). I provided filtration and some areas for her to get out of the water and she was soon exploring and eating. I added extra calcium (cuttlebone) in her food dish. About three days later she released her eggs during the night (at the new moon) and she was cleaning her front when I found her. I found it possible to see the young in the hatching tank by holding a flashlight to the glass. They were light in color and anyone trying to do this will see them better against a dark color. I couldn't get a photo of them since they were so small. After that I moved her into a three gallon tank with land areas and a filter with the thoughts of that being a place for her to be left alone to eat, etc., with no competition. The water was the same brackish strength as the water in the main tank, came from a mature aquarium, and the filter should have been mature at this time. <Very good. Necessary> Now as luck would have it all these events coincided with a gasoline shortage where I live that lasted more than a week. This figured in my not being able to get all the things I should have, ideally, had on hand for the hatching tank. I used phytoplankton (I have since read that zooplankton would've been better?) <Yes... actually both... the phyto to feed the zoo-> but by day five there were very few left though some were noticeably larger as if they had went through a molt or something. By day six they were all gone. I kept a day by day account of all this that might help me in the future if I decide to try again with a larger hatching aquarium and a heater to prevent fluctuations. I did get the surprise of seeing the male and the other female (the larger one) in the main tank mating right out in the open. Their burrows had been messed up in the reservoir incident and maybe that is the reason for their, uh, lack of modesty. So, of course I took photos! <Heeee!> The male doesn't seem to give this larger female any trouble, but then again she is larger than him. Sadly, less than two weeks after releasing her eggs, I found the little female dead (definitely) on land in the hospital tank. The past two days beforehand I didn't see her eating and she wasn't as "all over the place" as usual. In a way she was my favorite of the three, partly because of sympathy about her initially missing a leg and also because while the other two had made burrows, she was always out roaming eating more than the others and taking shelter under whatever was handy instead of having a more permanent home. I know Fiddlers are said to have short lives, but I would think that if she had lived out a full lifespan she would have been larger. <Mmm, size/growth a matter more of food, conditions, than age> Now I'm a bit paranoid about the two I have left. As expected, the larger female has developed eggs and I am anxious to see if she will release them on the full moon (versus the new moon, when the other Fiddler released hers). Since losing my favorite, I don't know if my heart is in trying with another batch of zoea right now or not. Any comments or advice will be appreciated. Thank you for your time, Crab Enthusiast <Thank you for sharing... please do continue to report your experiences, observations. Bob Fenner>

Crab Questions, brackish sys. 9/23/08 I have three Fiddler Crabs (Uca minax I am almost certain, one male and two females) and they live in a 2/3 land setup in a ten gallon glass rectangle aquarium (or paludarium, if you prefer). The water is about two inches deep (just enough to allow for a filter and also a circulation pump) and they have sand for burrowing. Under the sand there is a layer of gravel, and I have a small reservoir in the corner on the land side into which water is continuously pumped via tubing running from the water portion. The water moves out of the bottom of the reservoir, flows through the gravel and passes under the retaining wall (about 1/4 inch gap) and back into the water portion. The water is brackish (made with Instant Ocean) and I have a fresh water dish on the land portion that I also use for a food dish. If Uca minax ranges from Texas to Maine on the eastern coast of the U.S., at what temperature should they be kept? <Likely "room" is fine throughout the year, with some sort of cover/barrier covering most of the top> I live in the Carolinas and though it has been hot for months the room in which these Fiddlers are kept is about to get chilly. <As it is in the wild> I have their home on a sturdy wheeled cart so they can be moved. <Neat> If a heater is necessary could I use one of those flat, submersible heaters that are meant to be placed in a fish bowl under the gravel (no experience with those)? <You could... See Dr.s Foster & Smith re> I notice that under-the-tank heaters warn (after you open the package) that they should not be used on aquariums that contain water because the tank could crack. <Mmm, there are some low wattage ones that are fine here> Another temperature issue is that one of the females had eggs and must have released them (no sign of anything in the water, only the tiny white things that already live there), and now the other female is carrying eggs also. I have looked at everything I can find about what I need to do to attempt to raise a batch (quite a long shot, I know) and I am probably about to purchase some phytoplankton, Artemia hatchery, etc. in hopes of giving it a try (I have a small spare tank running for this purpose). <A worthwhile venture> In the past I received great advice from your site about three Blue Legged Hermits (Clibanarius tricolor) that I have been maintaining alone in their own aquarium. What is the ideal temperature for them? <Seventies F.> What is the best way to go about dosing such small systems with something like Kent Marine Super Iodine? <Dilute in new water just ahead of water change-outs> Or is that impractical for the amount of water, the Instant Ocean providing enough trace minerals, etc.? <Is likely adequate... no need to supplement.> Thank You, Crab Enthusiast <Welcome. Bob Fenner>

Fiddler crabs versus peacock eel 10/21/08
I have a freshwater tank with three gold fiddler crabs, one male and two female.
<Uca spp. are brackish water animals... don't last long in freshwater conditions... On the plus side, at least some Spiny Eels tolerate brackish water well, and may even be healthier in it than freshwater.>
Well I got a peacock spiny eel, who was about 5 inches, and the next morning he was being eaten by the female crabs.
<The eel died; the crabs ate the corpse. Spiny Eels die very easily, frequently from bacterial infections. For example, they can't be kept in tanks with gravel. Must be sand. Gravel scratches the skin, allows bacteria to get past the mucous layer, and within days they die. This happens SO OFTEN that it is depressing. Brackish water around SG 1.003 (as opposed to "teaspoon tonic salt per gallon" nonsense) may be beneficial to Spiny Eels because it minimises the risk of bacterial infections.>
I don't understand what happened. He was perfectly fine all day long... and I know that my tank is in great condition.
<Do you have sand or gravel in the tank? If gravel, that's likely part of the issue. Spiny Eels are also easily starved. You can't keep them with things like loaches and catfish because they don't compete for food. If you stick one in a community with loaches and catfish, it will get steadily weaker with time. They obviously don't eat flake or pellets, and need a meaty diet of things like earthworms or frozen (not freeze dried) bloodworms. Just getting food into them is hard enough without keeping them with other nocturnal fish that steal the food first.>
Is it possible that the crabs could have killed the eel?
<No. Uca spp. are primarily detritivores, though they will eat carrion.>
The eel was somewhat slow moving and was still very young. I am very upset about the eel, it was very beautiful and I would really enjoy having an eel in my community tank.
<Sadly, these aren't "easy fish" and I'd encourage you to read my thoughts here before doing anything else:
<Cheers, Neale.>

Please Read ASAP... Fiddler crabs... missing legs... poor English... too typical no reading, understanding of animals needs 8/5/08 Yes, <Yes?> I would like to know if you could help with my fiddler crab... I just bought it 2 days ago and I have just notice... that its missing 3 legs...yeah....where he has his huge claw. which I know its a male. <Likely shock from poor handling, maintenance. Will grow back if looked after properly. Fiddler crabs (Uca spp.) are of course BRACKISH to MARINE water organisms that shouldn't be kept in freshwater tanks. They need more land than water. Like to burrow. Keep in an vivarium (not an aquarium) with maybe an inch or two of warm (~25C) brackish (SG 1.005-1.015) water with a big sand bank (coral sand and silica sand mixed 50:50). Stabilise the sand with bogwood roots and various stones, ideally calcareous ones like tufa. Fiddler crabs are NOT compatible with fish. Period. They are too easily damaged by them, and aquarists that are keeping fish invariably have the wrong tank for Fiddler crabs. Fiddlers are omnivores and need a mixed diet containing small invertebrates and algae. Bloodworms, Sushi Nori, catfish pellets, algae wafers, etc. would all work well. Gregarious; keep in groups of six or more, with more females than males. Males will display to one another but rarely cause physical damage if given adequate space. Great escape artists!> Can you please help me I don't know what to do? should I return it. <Hope this helps, Neale.>

Mangrove "swamp"/ mudskipper, fiddler tank? 7/31/08 Hi Crew (or should I say crew member), This is 40 gal des (not sure anyone remembers her). I have a bee in my bonnet (or perhaps gobies) as I have a new project idea. My tank has been fallow for ages now, and I was paging through the book by "The Complete Aquarium" by Peter Scott. Anyway, I came upon the Mangrove swamp with the mudskippers and fiddlers and I was utterly charmed. <It is indeed a lovely aquarium.> Anyway, I have been researching this topic-- where to get the critters and plants, how to raise mangroves, what to put in the tank, how much water and sand, brackish, the range of topics. But a few things seem blurry to me (well more than a few...), but I 'll try for brevity. <Would highly recommend looking over Richard Mleczko's chapter on mudskippers in my 'Brackish-Water Fishes' book. He's easily the world expert on keeping these fish in captivity, and discusses every aspect of their care as well as all the different species you'll see on sale. In fairness, the chapter on Mudskippers in the Aqualog Brackish Water Fishes is also very good.> So here it is-- Basic setup: 40 gal breeder and stand; Orbits' compact florescent (2 92 watt bulbs). Plans: Replace actinic bulb with 6700K and keep the 10,000K. <Do make sure the tank is "mudskipper-proof", as these fish will climb out of any gaps they find.> Divide tank roughly in two with plastic, rock up to about 8 inches or so. Place (no.? ) potted mangrove trees grown from seeds (already with leaves, etc) around mostly one side. <Mangroves grow very slowly, and you may find plastic plants or houseplants in plastic pots (to keep the salty water out) will work at least as well. Plants like Philodendron work very well for this sort of thing.> Fill around with (? type sand-- oolitic, aragonite, etc?) about one inch on one side and about 1/4 to 1/3 on the other <Sand type doesn't matter, but a mix of coral sand and smooth silver/silica sand is probably the best in terms of appearance and "stickiness". The coral sand will also add a bit of buffering to the system.> fill with brackish mixed water 1.05 or so salinity (I have an RO system), over the top of sand on both sides. <SG 1.005 upwards to seawater is fine; 1.05 would be hypersaline and deadly!> Use small internal power filter and guarded 50 watt or smaller heater ( although I'm going to bet it isn't going to go on much). <Would highly recommend an external heater to avoid problems with mudskippers climbing onto a glass heater and scalding themselves. Failing that, make sure there's a plastic guard around the heater. But seriously, undertank heaters similar to those used for amphibian set-ups would be better. Filtration is relatively unimportant to mudskippers because they spend so little time underwater, so use whatever suits your budget.> Aquascape with some large flat rocks, coral pieces, shells, and driftwood (a little!). Cover with bullet proof plastic (I don't expect it to get shot, but it doesn't warp.) Cycle. <Always a good idea cycling the tank before putting in fish, but funnily enough Mudskippers are ammonia-tolerant "right out the box", presumably so they can survive in their wet burrows while the tide is out. They also spend most of their time on land, so aren't exposed to the ammonia anything like as much as regular fish. So provided you did lots of water changes so the ammonia stayed below 0.5 mg/l, you could probably cycle with the Mudskippers.> Add quarantined (? number of mudskippers (P. kalolo) and fiddlers (and ?). <Richard isn't a fan of mixing crabs and Mudskippers, so be careful here. Big crabs will nip small Mudskippers, and big Mudskippers will eat small crabs. Fiddlers are probably the best crabs to go with because they're deposit feeders rather than omnivores, but be careful. Periophthalmus kalolo is a fairly aggressive species, so either avoid having more than one male or else overstock the tank so no single male becomes hyperdominant.> Pull up a chair in front and watch! <Sounds about right.> So maybe my questions are apparent here. 1. I was told to plant the seeds in a gallon pot, I'm guessing clay. Is this a good size. I think the pots sound like a good idea given the root strength. What do you think of the gallon size and how many do you think I should do in a 40. The picture in the book (which is a 40) shows four , and I don't think the pots are that big. I was thinking 3? <Mangroves are trees, so whatever you do with them and however you pot them, eventually they will get too big. I don't actually rate them highly for this sort of set up.> 2. What kind of sand? The book says silver, but I was thinking aragonite or even oolitic to keep pH high. <Without undergravel filtration, the buffering effect of a mound of coral sand is limited. Buffering is proportional to the surface area of coral sand in contact with moving water; in the case of a layer of coral sand without undergravel filtration, only the top grains of sand are in contact with moving water. So I'd not fuss about this issue.> 3. What rock is safe? I think limestone would help the pH, but I think granite is the most common, in the yard sort of rock (I don't intend to buy it.) Is there rock I should NOT use? (Obviously nothing that would be too sharp on the fish.) <Again, don't be too worried about the pH issue. Marine salt mix will buffer the water nicely, and if it doesn't, you can also add a bit of home-brew Malawi Salt mix to up the carbonate hardness. I've described this elsewhere on WWM: http://www.wetwebmedia.com/FWSubWebindex/fwhardnessfaqs.htm So choose rocks that look nice, aren't spiky or rough, and don't have metallic seams in them that might poison the fish/crabs.> 4. I know driftwood is acidic, do you think the other stuff would out weigh it? Do I need to add something for hardness, pH? I have B-Ionic. I was thinking though that that was a bit overkill. <Bogwood will have minimal effect. If it does, up the carbonate hardness as stated above.> 5. Stocking number? (mudskippers, crabs). Any safe critter to put in there. I am guessing I don't have room for much. <Mudskippers are funny about tankmates. Your best bets are things like small brackish water livebearers, perhaps Guppies or Limia. But big Mudskippers will eat small fish, while big fish terrify Mudskippers who view them as predators.> 6. Cycling? I have read not such good things about BioSpira, that it isn't refrigerated. I have never seen it refrigerated. Fish food? Shrimp? <Any of the above. Or just let nature take its course, using the Mudskippers or crabs.> 7. I live in the desert, should I think about a fog maker, to get up the humidity a bit? <The lid on the tank should take care of this automatically.> OK, I think that's enough. I was working on brevity. Thanks Crew!!! You are terrific! --des <Hope this helps, Neale.>
Re: Mangrove "swamp"/ mudskipper, fiddler tank? 7/31/08
Hi Neale, Thanks for the great information. <Would highly recommend looking over Richard Mleczko's chapter on mudskippers in my 'Brackish-Water Fishes' book. He's easily the world expert on keeping these fish in captivity, and Just ordered off Amazon. <<I am sure you will enjoy.>> > <Do make sure the tank is "mudskipper-proof", as these fish will climb out of any gaps they find.> Yes, I have kept Jawfish. Tricky little devils. Fortunately mudskippers aren't $180 like those cool blue spotted Jawfish. Just when I thought it was safe to remove the netting around filters and the like, he jumped to his death! So no more removing netting, though without hang on the back stuff should be easier really-- until trees grow. <<Ah, seems you're mentally prepared at least! The difference is that Mudskippers are gobies, and are equipped with a neat suction cup that lets them climb up vertical surfaces, including glass.>> <Mangroves grow very slowly, and you may find plastic plants or houseplants in plastic pots (to keep the salty water out) will work at least as well. Plants like Philodendron work very well for this sort of thing.> The way I read Scott's book, it was the ceramic pots and not the actual trees that kept the bank up (along with rock. So you are really not depending on tree growth. <<I have the book and checked. My issue with ceramic pots is they're porous, so will let salt in. If you're growing salt-tolerant plants like mangroves or Nypa palms or whatever, then use whatever pots you want.>> > <SG 1.005 upwards to seawater is fine; 1.05 would be hypersaline and deadly!> Oh yes, woops! It's not a typo really, but I am familiar with all this. Just will have to go through the numbers again. <<Good.>> Thanks for advise on filtration and heaters! >below 0.5 mg/l, you could probably cycle with the Mudskippers.> Cycle with fish! Yikes! This is new info and I have never seen this (though saw they were tolerant of ammonia. <<Some mudskippers will happily frolic around sewage outfall pipes. They are incredibly tough fish.>> What about quarantining these guys (gals)? I have a ten gal QT. I was thinking in terms of about 2-4 inches of water and some rocks (or maybe dinner plates. <<Since they're the only fish in the tank, quarantining them is redundant. Of course you can't use formalin or copper medications in a system with crabs, but brackish water will kill off Whitespot anyway.>> > Periophthalmus kalolo is a fairly aggressive species, so either avoid having more than one male or else overstock the tank so no single male becomes hyperdominant.> What's your definition of overstock of P. kalolo in a 40? <<Depends on the size of the fish, and how much land there is. Richard's basic idea is that if all the fish are crammed onto the same bogwood branch or sand bank, none of them can make a territory. I'd be looking at half a dozen specimens, at least.>> Or can you sex the fish to determine which is male? <<Difficult to sex Periophthalmus spp. except to say males are more aggressive!>> Also I was told to overstock the crabs. Both because they are aggressive, and because some will be eaten-- this from a guy who does barbarus which are even nastier. <<P. barbarus usually ends up being kept alone.>> > http://www.wetwebmedia.com/FWSubWebindex/fwhardnessfaqs.htm Thanks for the link. > <Hope this helps, Neale.> You're all great! <<We do try.>> --des <<Cheers, Neale.>>

Fiddler crab not moving, feared dead. 3/6/08 Greetings Crew! I have a brackish tank with 4 Fiddler crabs (3 until yesterday, when I rescued another from PetSmart) I have had 2 of the crabs, a female and male, for longer than a year with everything ok. However, I woke up this morning to find the older female back-down with legs in the air...er, water, and not moving. I got her out, moved her around, tried to provoke a response, but nothing. I don't want to get rid of her for fear she may be molting, but if she is dead and I leave her in she will foul the tank. She has been this way for over 12 hours. Thanks for your help. Phillip <Hello Phillip. Sounds as if she is dead. Even when moulting, crabs have mobile mouthparts and gills. So if nothing is moving at all on your crab, she's probably dead. There's some reports that Iodine is a critical supplement that needs to be added to aquaria for crustaceans to do well in the long term. It's an inexpensive addition you can buy from any store catering for marine aquarists. Certainly worth a shot to see if that improves things with the remaining crabs. Do also bear in mind that Uca species only live for about 18 months in the wild, so anything beyond that in the aquarium is a bonus. Cheers, Neale.>

My crab isn't moving, BR 1/1/08 Hello crew, <Greetings and happy new year!> I was wondering if you would be able to help me out. I have a crab (*Seserama bidens*), sold to me as a Red Claw Crab. <Ah yes... now known as Perisesarma bidens, though the red-claw crabs traded may be multiple species, given that Perisesarma bidens is primarily from East Asia while most exports are from Southeast Asia and elsewhere.> I bought it close on a month ago and he quickly became my favourite addition, roaming about searching for food and generally acting in a brazen manner. <Quite so. These are rewarding pets when cared for properly, and well worth their own specialised quarters.> However, I recently purchased a 30 gallon tank filled 2/3, bogwood creating a land area and a rock pile for my two crabs to hide in (the other being a golden fiddler (*Uca *sp.) ) and for my dragon goby (*Gobioides broussonetti*). <A nice collection of livestock.> The new tank seems healthy (specific gravity at 1.005). that's the only real thing I measure) the guppies and platys that share it with them are doing fine, and the fiddler is quite lively. Crushed coral for substrate, java fern floating around, trying to get some pieces to take root. <All sounds fine, though strictly speaking Platies aren't brackish water fish, though my experiences agree with yours that they do well at low salinities.> The problem is the red claw, who used to be quite active, scavenging around his log as well as in the water, recently took to hiding. I assumed it was just molting, and after maybe three days, and no actual result, I picked out the rock he'd been holding on to from the rocky pile as he had not been eating or moving and I feared the dragon, who also likes that spot, might stress him out. <Curious. I'd have associated hiding behaviour with moulting, too. Crabs of most sorts are potentially antagonistic towards one another, so do check there isn't bullying between the Perisesarma and Uca crabs.> He looked just as he always did, no colour change, nothing that would indicate molting to me. As I have mentioned he used to spend a good bit of time on land, I thought maybe he just couldn't get up there now (he'd been missing a leg upon purchase, I know it's a no-no, but he was the only one left, and I hadn't really noticed till I got him home). <A missing leg usually isn't a problem when these crabs; they're quite tough and regenerate lost limbs quickly when kept in brackish water. On the other hand, our ability to prevent secondary infections in invertebrates isn't good, given that things like copper are toxic to crustaceans even at very low doses.> So I slipped him onto the wood and sprinkled a few bloodworms in front of him, he stayed for a while and then crawled off and fell into the water where he landed upside down. Despite much flailing he was unable to right himself, so I stuck the net in and he quickly righted himself. He's been there in the open, next to a large shell for over a day, not really moving and I still haven't noticed him eating. He's not being bothered by any of his neighbours. What do you suppose is wrong with him? <Very difficult to say. One problem with these crabs is they're often traded as freshwater animals, and if they've been kept in freshwater at the wholesaler and the retailer, then they can lose condition. Uca crabs are much worse in this regard than Perisesarma, but it is still one more factor beyond the aquarist's control. We don't really know anything much about secondary infections or parasites of crabs. Pretty much they're either healthy or dying. If yours is going to recover, it will, but otherwise the best you can do is watch, keep the water clean, provide suitable food, and if the crab dies, remove it at once.> My mother keeps telling me he's dead, and I try to tell her he's just molting, do you suppose this is so? He'd often sit for a while not moving before hand, but never for days! I don't really know what's typical molting behavior for crabs, I'd always thought they hid away after they molted, or during, not beforehand. <Moulting is very obvious and usually over in a couple of days. One problem with crabs and indeed freshwater crustaceans generally is iodine. While small shrimps seem to get enough iodine out of the water or their food, larger animals like crayfish and crabs apparently benefit from iodine supplements. These supplements can be purchased from stores catering to marine aquarists as iodine supplements are widely used in reef tanks. At this point it might be too late for the red-claw crab, but any new specimens you buy, and the Uca crab as well, will benefit.> I wouldn't think it would be a problem with my levels, as the fiddler and everyone else are doing fine. I heard a rumor of Java ferns being poisonous to fish, he ate a good chunk of one before I moved them, could that be a factor? <Possible, though normally animals stop eating the Java ferns because they taste nasty long before they actually get sick.> I'm just trying to think of everything here, no matter how absurd. I apologize for my lengthiness, but the instructions on your site said include every detail. Any thoughts would be well appreciated, -Collin <Hope this helps, Neale.>
Re: BR crabs... Now: Specific Gravity 1.010... for Hermits, Dragon Goby... 1/2/08
Hello there, <Hello Collin,> I wrote in yesterday about a crab who's not up to his norm, and I will for sure be trying to track down an iodine supplement (as recommended by Neale) to help out at this stage, whatever good that will do. I had heard about this, but there is a slight lack of aquarists specializing in crustaceans or BW tanks in my area and I couldn't find anything locally on it, but I know of one place that probably has it and knows what they're at. <Anywhere specialising in reef tanks should have this, and failing that, you could obtain online.> But! I have another question: I read on your site that the blue-legged hermit crab (Clibanarius tricolor) could be acclimatized to a specific gravity of 1.010 <Apparently so. Do acclimate them carefully, and take great care to identify the crabs carefully before sticking them in a low-salinity environment. SG 1.010 is at the low end of their range, and you will of course need to make sure other things like water quality are "marine standard".> I was wondering if you could tell me if the inhabitants of my brackish tank would be fine with this level of salt, as my findings on the internet have been rather inconclusive with different authors throwing numbers around as if they were just that: numbers. There doesn't seem to be any set specific gravity that people can rely on for these animals. <Uca and Perisesarma should be fine; both spend minimal time in the water and likely breed in the sea anyway. If you're concerned, put a small basin of plain freshwater for them to drink somewhere on the land. An upturned Oyster shell stuck in the sand would be ideal. Guppies can be acclimated to anything up to full strength seawater safely, but you must do this very slowly, over several weeks. You can actually buy "marine guppies" as feeders for marine fish. The Dragon goby will be very happy at SG 1.010. The only chap who can't be kept there is the Platy.> Anywho, my tank has a golden fiddler (*Uca *sp.), dragon goby (*Gobioides broussonetti*), Red claw crab (Perisesarma bidens), two guppies and two platys. So I was wondering if you would be able to tell me if I would be able to house this little guy sometime in the near future with the current inhabitants, maybe rehousing the guppies and platys? Also, would I be able to add the hermit with the current bottom dwellers that are on the go in there given this is all a 29 gallon tank? I may be short one red claw crab within the next week or two, if that's a factor. (Given his current condition. <I would imagine they will ignore each other. Hermits are too well armoured to be molested by small crabs, and since the hermit is fully aquatic, your land crabs won't encounter them much anyway.> Though I was watching him "scratch" his claws off one another, and against his legs. I know the fiddler and red claw both came from the same tank, same store, only the red claw had been in there about a month later till I bought him, I hadn't really been counting. Could have been FW, I wouldn't be surprised, I'll ask them soon.) <Usually these things are sold as freshwater.> So yeah, thanks in advance for reading my email, You guys are awesome -Collin <Glad we could help. Cheers, Neale.>

Clibanarius tricolor biotype 1/14/07 Hello Robert, <Neale> I can probably rustle up a few pictures. There are also some useful sources on Wikipedia, which we used in my book (which I finally have a preview copy of, by the way). So there's other options, too. <Have the ones you sent along, thanks. Will post with credit to you> Since you're a marine guy, perhaps you'll know whether the blue-leg hermit sold in the UK (Clibanarius tricolor) is the same as the one in the US. I've mentioned it in the article because it does well down to SG 1.010. I assume it's a rocky shore or estuarine species that gets collected as a cheap reef critter. But I don't know anything specific about its ecology. Can you enlighten? <I do think this is the same animal/species... and yes to its euryhaline tolerance> Cheers, Neale <BobF, out in HI... trying to catch up!>

Fiddler Crabs 12/14/06 My son brought two fiddler crabs home from school after a class project. We have tried to learn about them from internet searches, but only recently found your web site. It has some great information! <Ah, good... We intend to be useful (timely, accurate, significant, meaningful... in our information presentation... And always open to review, suggestions for improvement> We've set up a small tank with aquarium gravel, and we set a 3/4" deep dish (actually the bottom of an old pencil case) in the center. We've added some plastic plants and a small aquarium feature, which the crabs seems to like to hide under. We keep gravel and brackish water in the dish. We feed them ground hermit crab pellets, bits of krill, and bits of cuttlefish bone. I remove approx. 1/5 of the water every night and replace it with fresh, and clean the tank every two weeks. <Sounds very good> We've had the crabs two months. At first they were very active, scurrying around the stones at night. Now they seem to spend all their time in the water, hiding under the tank features. <Mmm, not atypical behavior. Are shy animals that don't like a lot of "commotion"> They became active again a few days ago when I cleaned the tank, but soon went into hiding again. In the time we've had them, they have not molted. <Will do so in time... with growth> Does this sound like normal behavior? <Not unusual thus far> Is there something more we should be doing? <Do you know, have you tried to find out the name of the species you have? Some fiddlers have quite different requirements... e.g. the saltiness of their water...> We really like the little guys and want to take good care of them. I'm not prepared to invest a lot of money in equipment, but would at least like to know what I should be doing. Thank you for your help! Mary <Please consider setting your child on the task of discovering the species involved here... And write me/us back re your progress. Bob Fenner> Re: Fiddler Crabs 12/15/06 Thank you! I will share your reply with my son and set him upon his research task! Mary <Ah, good. BobF>

Dismembered crab 11/28/06 I suspect this question will end up being mostly academic because I have a feeling the critter in question will be an ex-critter by the time I get home. I've got two red claw crabs <Likely Fiddlers, Uca> in a 25 gal. brackish tank that had, up until last night, coexisted just fine. They had established separate territories and mostly didn't interact at all. Well, I added some new plants last night and this morning awoke to a crab devoid of its pinchers. Completely amputated cleanly at the joint with the body. It was flailing around upside down and couldn't right itself. I moved it back up to its territory and placed it somewhere where it was hidden and mostly upright. As I said, I'll be surprised if it survives the shock, but if it does, is there anything I can do to help it survive until it molts and starts to get its front claws back? <Separate it from the other conspecific crab> I know that those claws are what it uses mainly to feed itself and it doesn't seem to have alternative legs that it uses like our crayfish do. And would adding something like Melafix make any difference? <No to adding this or any other phony or real medicine... time, feeding, keeping the water quality constant... When the crab molts a few times, it will re-generate its missing limbs. Bob Fenner> Sarah
Re: Dismembered crab 11/28/06
Thanks for the suggestions. And no, it's not a fiddler, it's a red claw crab, Sesarma bidens or whatever they've changed the taxonomy to. Sarah <Ahh, thank you for this. My input remains the same. Bob Fenner>

Brackish Fish and Crabs - 3/5/2006 I am very interested in having brackish crabs and brackish fish. I have not bought a decent sized tank yet but I want to research types of fish first. I like puffers (who doesn't) but obviously, they cannot go with crabs and the like. <<Depends on the personality of the puffer, but you are right, as a rule.>> I have gone on very many internet sites and they sometimes have information on brackish crabs and fish in the same tank, but only ever say top dwelling fish and short finned fish. One of the only examples of brackish fish and crabs was red claw crabs and bumblebee gobies but those are bottom dwelling! If possible, could I be told of all possible combinations of fish and crabs (in brackish conditions) including more than one type of fish to one type of crab? <<Too many variables, you are going to have to do your own research here.>> I like red claw crabs but would go for another like fiddlers. I would only aim at having one or two crabs in a tank. To make a more specific analysis of what type of tank I am after I would have to say an around 50-gallon tank with a lot of depth and width (not much of a tall tank person). For internal decoration and design, I would like to have a fake rock cave with its entrance facing the front of the tank so I can still see the crabs inside (maybe logs so they can reach the air not sure yet on what add so they can reach) <<Do make sure you house the crabs you choose properly, and create a dry land area, if necessary.>> I would really like to know some names at least of some top dwelling short finned brackish fish. If there are no good combinations, if possible, could I be sent a table or something in which it shows what brackish fish can go with what? <<No such table exists, sorry!>> This is a lot to ask but it would be extremely helpful and I may have asked things against your policies (apologies if I have) but I saw that I had to type properly and I hope I did so adequately. <<Capitalized I's would be nice too.>> I will not expect a question this long to get a full reply instantly and I do hope this is a free service otherwise oops. <<It is, yes.>> Yours sincerely and thankfully whether I get the things I asked for or not (very long message to read), James Briscoe <<Look into Orange Chromides; they are a beautiful low-end brackish Cichlid. Good luck with your research. Lisa.>>

Marine Inverts in Brackish Aquaria? - 01/03/2006 I've looked all over the web on this question. <All of it? It's a big place.> So ya'll are my last hope on this one. <I'll see what I can do Obi-Won...I mean Michael.> I have a light brackish 29 gallon with an Archer and a Leopard Puffer. My question is can I buy a saltwater crab and acclimate it to my tank. <Generally speaking; no. Reef Invertebrates come from one of the most stable environments and can not adapt to such a change.> I am willing to increase my salinity, if need be. <Research WWM re: the proper environment for marine inverts.> I know puffers eat crabs and snails, however mine is pretty small and well fed with lots of cover in tank for hiding. <You'd be surprised how much damage that little beak can do.> Maybe a larger crab or hermit? <See above.> Thanks, Michael <Welcome, Adam J.>

Crabs & Puffer? 5/31/05 Howdy, <Hi, Pufferpunk here> I am wanting to add a brackish water crab that can stay in the water all the time in my 10 gallon tank. A blue legged crab was a thought, but I'm not sure he can stay in brackish water. The other part of the problem is that I have a figure 8 puffer in there too. I'm thinking the puffer will eat a blue legged crab even if he could survive the water conditions. I've read plenty of websites that just say nothing can go in with the puffer (crabs and other cleaners that stir up the sand). For a small tank with only 1 fish, I wanted some other small creatures to climb on the liverock and stuff. Needless to say, snails are out of the question. Any suggestions? <Crabs & snails are puffer food. I don't suggest adding anything a puffer can eat. There really is no clean-up crew for that tank, you'll have to do your own maid service. In a 10g, it is best to keep the puffer alone (interesting enough tank w/just the puffer) but you might be able to get away with a couple of bumblebee gobies as tank mates. They may get eaten though, if that is the kind of F8 you have. You just can't tell with a puffer! ~PP> Thanks, Brian

Fiddler Crabs on the Lam! I had 2 fiddler crabs, both tried to escape the tank, one did. <Yes, they are great escape artists. Best to keep the water level down a couple of inches & keep a tight fitting lid on top, taping off any entrance for cords, etc, where they can climb to get out.> I have read that they sometimes require time away from water but must be kept moist. I have mine in a deep 40g. tank, how often should I remove him and for how long should I keep him out of the water? Does this require a separate tank? <A floating piece of driftwood or plant should suffice.> I have only had these for about two weeks but would like to keep the one I have left, and hopefully from escaping! I still haven't found the other one! <I have found them on the opposite ends of my house, from where they escaped & my dog has found a few! ~PP>

Red Claw Crab <Hi Anthony, MacL here. The only red claw crab I know of is actually a brackish crab often sold for freshwater. Is this what you have?> I purchased a red claw crab from a local Fish store about 2 weeks ago. I believe the crab is a female due to the very small claws. Anyway, recently she has had her abdomen hanging open. <Maybe releasing eggs?> I figure she was getting ready to molt, but she hasn't done anything for 2 days now. She has already molted once since we have had her and it didn't take long. She has plenty of different kinds of food. Also these past 2 days she is flipping herself over on her back. <Not a really good sign.> Can you tell me what is wrong? <I'm just guessing here but I think you probably have her in fresh water and she needs some salt. I also think it might be a difference in PH as well.> I have searched through the internet, but cannot find any information on Red Claw Crabs. <I did a search on google and came up with tons of thing on them. You might try www.google.com> Thank you for your time and patience. <Anthony you might do the research on them and decide if it needs to be in brackish water or not and make a decision from there.> Anthony <An excellent site re this species: http://wrongcrowd.com/aquaria/crab/ RMF>

Rogue Crab >Hey WWM crew. >>Hi. >I have a slight problem. >>Me too, but I'm not going to talk about it right now. >My red clawed crab has decided to take a walk on the dry side of the tank. >>The "dry side"? As in "the outside"? >I have spent two days looking and am at a loss as to where it is. >>What kind of crab is this, exactly? A land hermit crab? A saltwater hermit crab? A freshwater fiddler crab? Is it a tasty crab, maybe? >Two questions. Will it still be alive this long outside the tank? >>I have no idea, since there are so many crabs we can be talking about, here. If it's a land hermit, and you're keeping it in a tank with NO dry areas, then it's off to find a new flat, better digs and all that. Otherwise.. >And if so, how in the HELL do I track the little bastard down??? >>Find a sexy girl crab, maybe? >I'd like to find him before the cats do, and if he's perished I'd really rather not find him by smell. >>What if the cats already found him, and that's why you can't? >Any help you can pass along would be greatly appreciated. Thanks, Keith P.S. Don't tell my wife..... >>Mum's the word! I'd start checking the kitty dumplings, myself. Marina
Rogue Crabby FOUND!
>Dear crew, Crab found!!! >>Hee! Great. And don't say I spilled the beans to your wife! >More importantly, ALIVE!!! Apparently it had been living in the power filter for the last week... >>Must like it there. >So now, what do I do with it? >>Scold it. >It's not a hermit, but I don't know much more about it than that. It was sold to me as a "red clawed crab," I didn't read the scientific name. Didn't think I'd need to. Best descript. I can give is that it's about 3/4" across the back, and is shaped like a big brown Chiclet (gum), with arms and legs. It has darker brown patterning over a lighter shell, with two big red pinchers up front that are white on the tips. And it's freshwater. >>That's somewhat helpful. >I've offered meaty foods, but it's never showed much interest. Could it be wanting algae, or just anything that's decaying enough to be tasty? >>That may be, or it's also wanting a private flat, a room of his own so to speak. If you don't mind it being in the filter, leave it there. If you do, then give it a hole to call home, and don't worry about feeding it directly at this point. You could try a few things, but let's try that first, see if it's happier having some privacy. When you scold it, don't wag your finger too close to those claws. Marina >As always, any help is welcome. Keith
Rogue Crab goes to the Rogue's Gallery
>Hey Marina, a parting note on my eight legged headache. >>I suppose he's too small of a bit of meat to be enjoyed that way, eh? >After much searching, I have a solid I.D., and another "fish experiment" to irritate the wife with. (Not to say she doesn't enjoy the tanks I have, she's even encouraging a saltwater project. But, She IS jealous of the time it takes to care for, and more importantly view them. And the only reason she wants marine is because she wants, and I quote, "Nemo fish." <sigh>) >>Oh lord, not Nemo again! (A tip, they do NOT need anemones!) >I have discovered myself to be the proud owner of one Sesarma bidens. >>A who? If you can possibly send in some decent pictures, we'd love to have them archived on the site. >A fresh to brackish species from southeast Asia. >>Ah! >Eats anything handy, as long as it's not moving. >>Thank goodness for that, and other small favors. >Not known for chasing fish, fortunately. Likes to trek out on dry land a few hours a day. >>So he might appreciate something more resembling a vivarium, or mangrove setup. >Smart, strong, fast, and hardy apparently makes for a notorious escape artist. But, at least I know why my filter cartridge lasted twice as long as normal, he cleaned it for me... Go figure. Looks like I'm entering the world of <GASP> species tanks! >>Sounds like every filter needs one of these guys. >As if my life wasn't interesting enough. Oh well, something new for the kids to poke at. Keith >>I like the way you think. Glad to know you've nailed him down, so to speak. And thanks for the follow-up. Marina

Brackish Arthropods and Catfish 7/11/03 What kind or kinds of crabs can live in a brackish water aquarium? <quite a few shrimp and crabs.. some of which are seen in the trade like ghost/grass shrimp, mangrove and fiddler crabs... none of which are compatible with your puffer which will pick their eyes out if not eat them outright> I currently have a 65 gallon tank with bumble bee gobies, green scats, puffers, and mollies. My tank has a sand bottom that needs some house cleaning. Got any ideas? S/y, Carole <The is an Albina (not "albino") Pleco that is brackish tolerant. A good scavenger and innocuous. Ships out of South America: http://amazingrays.50megs.com/custom2.html Best regards, Anthony>

Feeding (freshwater crab) I just got an aquarium, my first fish was the classic gold fish I just got two more fish and a crab, am not sure what kind but its small and has one big claw and one very small, <<Sounds like a fiddler crab, and depending which type you have may be better off in a brackish system.>> my question is am not sure what or how to feed it, I was told the shrimp pellets but it doesn't seem interested, am not sure if that's what I should be trying to feed it and if it would eat them after a while when I left it would never get a chance because the (small white fish with orange on its head) eats all the food as soon as it hits the tank <<Hmmm... most crabs are termed opportunistic omnivores, which means they'll eat just about anything they can get their claws on, which sometimes included each other, depending on the type of crab. I would ask the place where you got the crab what the Latin name is, hopefully on their shipping list, and use that to find more information about this crab. In the mean while, here is a URL to get you started: http://www.wetwebmedia.com/BrackishSubWebIndex/braccrabs.htm - and do read the FAQs beyond. Cheers, J -- >>

hi (Collected brackish crabs...) <<Hello...>> my name is Samantha. <<Mine is Jason - how are you?>> I went crabbing the other day and all the crabs we caught were to small to keep. when we got home my little sister asked how long does it take for a crab to grow an inch. I told her I' find out for her . so if you could please e-mail me that would be great. bye Samantha <<You sure asked the tough question... for starters, crabs and their other cousins in the Arthropoda family actually shed their skin in order to grow in a process called molting. So... the real answer to your question is: It depends on how often the crab molts. This can be once every couple of weeks to once a month or once every couple of months depending on the type of crab. Even then not all crabs grow to large sizes, some stay small. If you want to read up some more on crabs, here are a couple of links: http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabs.htm http://www.wetwebmedia.com/BrackishSubWebIndex/braccrabs.htm Hope that is helpful. Cheers, J -- >>

"A Craw-Fish by any other Name would Chew Plants..." Mr. Fenner: I am in the early stages of preparation for building my first community tank. I am planning a 35-Gal tank with many live plants and two species of schooling middle fish, one species of surface fish, and an additional species of bottom-feeding/Pleco-type fish. Is this feasible? <Sure> My main concern is this: I feel that in the future I may be unable to defend myself against the irresistible charms of lobsters and crayfish. <They are delicious... prepared properly!> Is there a place in a perfectly harmonic community tank for one of these invertebrates? <Mmm, no, not really. There are some fresh to brackish crustaceans that are "better"... please read: http://www.wetwebmedia.com/shrimpfw.htm> I hear that they have picky tastes in water pH and temperature, are destructive to aquatic landscaping, and can be determined to bust out and go AWOL. Is there a way to have fish AND Yabbies? <Again... not really... their tastes are actually "too cosmopolitan", and many species are known to be quite "eury" condition... adaptable to widely varying conditions... but most all what folks call "lobsters", crayfish, crawdads, ditch "bugs"... are all too destructive, fish-eating to be "harmonious" in a community tank... Maybe two tanks? Bob Fenner> Please advise.

Freshwater crabs Hello, I want to try keeping freshwater tropical crabs. The species that is often on sale in the UK, small red crabs. I can't find any books or articles on keeping them. I would like to know; 1. what they like to eat, 2. how many to a tank, 3. if I can keep a few fish with them as well, 4. how long they live, 5. what sort of tank (plants, rocks, shelter, etc), 6. ph of the water, 7. filtration, 8. how much oxygen, 9. and how simple they are to look after. Thank you <Hmm, I suspect it is Sesarma bidens you are referring to. Please start with this site: http://wrongcrowd.com/~aquaria/crab/ and use your search engine with the common and scientific names to find more. Some general husbandry information can also be found on our site: http://wetwebmedia.com/brcrabs.htm Be chatting, Bob Fenner>

I just got from our pet store tiny red claw crab now I cannot find out much about them & how to care for them they are not hermit crabs but red crabs I looked up res Caribbean crabs found nothing I need to know more what they need thanks Sharon >> Not enough information, I'm afraid. Maybe call, go back to the store, and ask them to check their invoice for the scientific name of these decapod crustaceans... And do keep your eye on the crab... Some get quite big, and many are opportunistic... eaters of other livestock they can get their claws on

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