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FAQs on Freshwater Crabs

Related Articles: Fresh to Brackish Crabs Freshwater CrustaceansInvertebrates for Freshwater Aquariums by Neale Monks, Forget Crawfish Pie, Let's Make a Crawfish Tank! By Gage Harford

Related FAQs: Freshwater Crabs 2, & FAQs on: FW Crab Identification, FW Crab Behavior, FW Crab Compatibility, FW Crab Selection, FW Crab Systems, FW Crab Feeding, FW Crab Disease, FW Crab Reproduction, Fresh to Brackish Water Crabs, FW Crustaceans 1FW Crustaceans 2, Terrestrial Hermit Crabs, & Marine: Hermit ID, Hermit Behavior, Hermit Compatibility, Hermit Selection, Hermit Systems, Hermit Feeding, Hermit Reproduction, Hermit Disease/Health, & Crayfish FAQs, Crayfish 2, Crayfish ID, Crayfish Behavior, Crayfish Compatibility, Crayfish Selection, Crayfish Systems, Crayfish Feeding, Crayfish Disease, Crayfish Reproduction,

Just a quick question, missing livebearers post holiday  7/14/07 Hi, I currently own a ten gallon tank with a few platies and a guppy inside it, along with a few platies that are small. I went on vacation and notice that a few are missing. <Sorry to hear that. Be sure and figure out *why* before adding anything new. Check water chemistry and quality, for example, and double check you're using the right food, i.e., something vegetable/algae based rather than generic flake food.> I think they might be dead, and I just want to know your suggestions on what might have happened... <No idea without more details. Water chemistry, water quality, number of each species, how long you were gone, what foods used, etc....> ...and what kind of crabs and shrimps are compatible with them. <None. Crabs are [a] amphibious so need somewhere to walk on land and [b] predatory. Shrimps can work with small fish but they are generally delicate and if you can't keep guppies alive then you're probably not at the stage in your hobby where buying shrimps would be worthwhile. That is, unless you don't mind the shrimps being dead in 4 weeks. Seriously, they need excellent water quality, the correct diet, and safe places for moulting where they can't be molested.> I usually leave fry in the tank instead of separating them and I want a few to live, are these good to add to the tank? <Don't understand this. Do you mean the crabs and shrimps are good to add to the tank? If so, no.> Or are they bad like Albino Aquatic Frogs? (I had bad experiences with them) <Not "bad" but just wrong for you and your aquarium. Crabs need their own vivarium a bit like something used for newts or frogs, with some water for bathing but also some dry land for social behaviour and feeding. Shrimps are really something for the semi-advanced hobbyist. Most of the ones sold end up dying within a few weeks when thrown into generic community tanks. Cheers, Neale>

Halloween Land Crab 03/17/07 Hi, thank you for taking the time to read this.  I have what the pet store called a Halloween Land Crab.   <Gercarcinus sp., maybe G. lateralis.> He is not set up in some amazing aquarium, he is just in a plastic cage.  I have a water dish for him that's 2 inches deep that he climbs in and out of.  The bottom of the cage is filled with calcium sand and aquarium pebbles.   <Ideally, he needs a sand substrate deep enough and just damp enough to burrow into, and needs enough saltwater and enough freshwater, each in separate containers, deep enough to fully submerge himself - though the land area is by far the most important.> He has been doing really well eating bits of fruit such as apples, oranges, pineapple and also an occasional guppy. <Needs more meaty foods, preferably things like human-consumption shrimp (raw, frozen and then thawed) and fish; krill, meaty fish foods, and also Nori (seaweed) would be other important foods.> But recently three of his legs fell off on his right side!  What is going on? <Likely he is very deficient in something that he needs - saltwater, perhaps, or iodine....  Feeding the foods mentioned above, especially shrimp, krill, and Nori which are rich in iodine, will be very important.  Supplementing the food with a reptile calcium supplement will be helpful, as well.> He was not in a fight with another crab and I've never experienced him going through the "shedding process"! Is he unhappy or sick? How can I tell what's going on? <sounds like a state of disease, not a normal molting situation at all....  I would urge you to improve this critter's living space and food.> If this is below what you guys do, then I'm sorry to waste your time, <A question is never a waste of time.> I just need simple answers and can't seem to find them anywhere. <Thank you very much for searching for your answers, and for asking questions.> Nick <All the best to you,  -Sabrina>

Amarinus lacustris, ID, habitat of a FW Crab from down under  03/09/07 Can you tell me what "Myth" was being referred to here in the question in the following paragraphs? If I understand correctly the myth was concerning Amarinus lacustris. I have been trying to get a few specimens of Amarinus lacustris for a long time. I try to track down every lead but this one is  too cryptic for me to figure out what was being referred to this time.. Michael Hissom Freshwater Invertebrates, ID? Hey guys I am  trying to ID a crab that is appearing more and more frequently in Australian  stores. It has been incorrectly identified by several stores as Amarinus  lacustris (Freshwater spider crab). I suspect the supplier is keeping this myth  alive *lol Anyway, the crab in question is often referred to as a "brown backed  crab". Orange/brown body with a chocolate brown H symbol on its shell. claws of  equal size and quite heavy set, not long/slender. It seems to get to about 2"  shell width. I would LOVE to know the scientific name for this little beauty, as  although I am sure I could keep it happy using general crab knowledge, it would  be nice to know its specifics. Sincerely, Abbey AKA  Callatya <Mmm... well... this could be Amarinus... Please read here: http://www.google.com/search?q=Amarinus+lacustris&rls=com.microsoft:en-us:IE-Address&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7PCTA ... and am going to send your query to our resident FW crustacean expert, SabrinaF for her input. Bob Fenner>

Land Crab Sickness  - 3/7/07 Hi, thank you for taking the time to read this.   <Thank you for taking the time to send it!> I have what the pet store called a Halloween Land Crab.   <Ah!  Gecarcinus sp., maybe G. lateralis.> He is not set up in some amazing aquarium, he is just in a plastic cage.   <Really better if he has a slightly damp sandy substrate deep enough to burrow in and sufficient water to completely submerge himself; preferably both a container freshwater and a container of saltwater.> I have a water dish for him that's 2 inches deep that he climbs in and out of.   <As long as he can completely submerge himself, this is okay.> The bottom of the cage is filled with calcium sand and aquarium pebbles.   <Moist, I hope?  And deep enough to burrow in?> He has been doing really well eating bits of fruit such as apples, oranges, pineapple and also an occasional guppy. <He'd do better to have a little more "meaty" food in his diet - bits of human-consumption shrimp (frozen then thawed, uncooked, preferably including the tail or shell), krill, etc.> But recently three of his legs fell off on his right side!  What is going on? <Possibly a calcium and/or iodine deficiency....  A diet containing more of these nutrients is important.  In crabs that are more aquatic, supplementing their water with these nutrients is very helpful, but in your more land-dwelling Gecarcinus, I don't think it would be beneficial enough to do so.> He was not in a fight with another crab and I've never experienced him going through the "shedding process"! Is he unhappy or sick? <More likely sick, I'm afraid.> How can I tell what's going on? <That's a tough question with no easy answer.  Unfortunately, there isn't much information about invertebrate disease.  The best we can do for them is to provide them the closest environment to their natural habitat that we can provide.  In the case of your crab, this means HIGH humidity, substrate to burrow in, and enough water to totally submerge itself when necessary.  I would fear that perhaps the humidity is the problem in this case, as you mention that he's in a very basic setup.  A 10 gallon tank or larger with a lid to help keep in humidity would be very good in this case.> If this is below what you guys do, then I'm sorry to waste your time, <There are no questions that are "below" us.  Your crab is important enough for you to write in, so it's important enough to us to help you!> I just need simple answers and can't seem to find them anywhere. <There are no simple answers with invertebrate pets, my friend.  I wish there were.  Try providing him a more humid environment and a diet with more iodine and calcium (again, shrimp with shells, krill - these will be helpful!) will likely be the best things you can do for him right now.> Nick <All the best to you,  -Sabrina>

Fiddler and hermit crabs in same home?   12/3/06 We have 2 hermit crabs and now my granddaughter has a chance to obtain a fiddler crab from her teacher at school. Is it possible a fiddler can live with hermit crabs? Please answer soon. <Mmm, is possible... though not likely within the exact same "habitat"... likely your Hermits are terrestrial (if marine, or land types, please see WWM re their care)... and the fiddlers are highly likely amphibious... need a saltwater environment to dip into at their volition. Behaviorally these species will likely avoid each other, unless their is a shortage of food. Bob Fenner>

Freshwater crab compatibility  - 11/11/06 Hi, I purchased a large piece of driftwood for my discus tank.  Later in the evening, I noticed that I was now the proud mother of a crab. 1. Is the crab compatible with my discus (7), angels (2), beta (1), Cory cats (2), and Gold Nugget Pleco (1) ? <... highly unlikely> 2. What kind of crab might it be?  I surfed all over the internet and can't find anything that looks like it.  I have determined that if it's a fiddler, it's female. <Uca likely... see the Net, Google images with this genus name> 3. it's brown in color to the reddish side.  The body is about 1/2 inch square.  Overall size is about 2 1/2 - 3 inches.  How big will it get? <Depends on the species, but this is likely near maximum> Thanks in advance for your help. Grey <I would separate this animal... Bob Fenner> Crab Eating Plec or is it Plec Eating Crab? - 10/21/2006 I have a rather large common-sail fin cross Pleco that is showing signs of discoloration and his armor it starting to stick out. I have tried krill shrimp to boost his color I have treated with a medication made for many illnesses including parasites and scaling. I even tried feeding him algae wafers. I am all out of options. I have seen that one of my fiddlers is missing can a Pleco eat a fiddler by accident if so can this make him sick? He is a male. I was also wondering if I need to get him a mate or another larger Pleco. I have tiny tot the baby Pleco, it is the same breed as he is, which by the way is fat and happy. I did put my Bettas in the tank with him while I cleaned their tank and the female is a bit more aggressive than the male which made them chase each other and the female beta did challenge big boy. Could they of stressed him out? I feel I am running out of options he's not even full growth potential yet, he's supposed to get up to 18 inches and he's only 10 could it be old age he is a rescue fish from a lady that didn't want him anymore. Do I need to get him more tank mates? Please help in stuck up the creek without a paddle... and need as much help as I can get. <It may be that a bit of crab shell is the underlying problem. Bloating is usually caused by either constipation or an infection. If this is a blockage, and he's still eating, you can try some fresh or frozen veggies. Shelled raw peas work well to get things moving. If he's not eating you can try adding Epsom Salt to his water. One heaping tablespoon per 5 gallons of water. For an internal infection medicated flake is called for. But only if he's eating. Internal infections that progress to a point where the fish is not eating are very difficult to treat. In that case your best chance is keeping his water pristine with very frequent (daily), and very large (50%), water changes and crossing your fingers that his immune system will kick the bug. I doubt a three inch Betta stressed out a ten inch Pleco. Also, there are no crabs that can live a full life in freshwater. So no more crabs, OK? Don>   This is the edited copy I am sorry I sent it before I checked last time I hope this is better on your eyes. <Thank you!>

FW Crabs, using WWM 8/2/05 I was wondering what kind of crab this is: little red things in fresh water tanks, they stay in water at all times. I discovered that PetSmart (the worst place for buying fish) had them for $2.00. Very good with plants, keep real clean, always picking out the dead parts and leaving the beautiful green foliage behind. They also eradicate those little pond snails too ^_^. I don't know what kind of crab these are, but don't put them in with Bettas, or slow moving fish. Polara_Blues <Please learn to use the search tool, indices on WWM... and read here: http://wetwebmedia.com/PlantedTksSubWebIndex/fwbraccrabs.htm and the files linked... Bob Fenner>

Crabby Compatibility - 07/14/2005 Hello: <Hi.> Are there any freshwater crabs out there that are compatible with African Cichlids? <Mm, no, not any that are available in the aquarium hobby in the US, in any case.  There are, however, some different crabs that do live in lake Tanganyika and are pretty neat looking.  I do not believe that any of them are exported for the aquarium trade.  Furthermore, I fear any of them would be quite capable of taking on most cichlids.  The crabs that ARE available in our hobby are all, with one exception, brackish to marine animals that absolutely require land masses (can't stay submerged 100% of the time).  The one exception, the Red Claw Crab (Pseudosesarma moeshi / Sesarma bidens) can survive with only freshwater access, but still requires a land mass.> Thank you! Pedro <Wishing you well,  -Sabrina>

Online Freshwater Livestock Store? - 08/19/2005 What is a good web site to order freshwater fish/snails/crabs online? <As far as fish are concerned, you might try http://www.liveaquaria.com/ .  Crabs - please keep in mind that there are NO truely aquatic, freshwater crabs available in the hobby in the US, to my understanding....  ALL are brackish to marine animals, or absolutely require a land mass....  For some pretty neat fish and inverts, http://www.franksaquarium.com/ .  Some really awesome North American natives can be found at http://www.jonahsaquarium.com/ .  Hope you find what you're looking for!  Wishing you well,  -Sabrina> Crabby Conversion? - 08/07/2005 Can saltwater crabs adapt to fresh water? <Unfortunately, no.  Thanks for writing in!  -Sabrina>

Answer to a mystery query (FW crab) 8/26/05 Bob: <Actually, Sabrina with you, today> In answer to Sabrina's question about the "red crab" on http://www.wetwebmedia.com/swcrabidfaq3.htm from 8/13/05, I believe I have the answer. <My question??  Oh - OH!  I see.  Yes, that was in reference to the surrounding entries ("Mystery Crab") that I was helping Charlotte with.> I too bought what the LFS was calling a "fire crab" (or so it sounded with his slightly different accent from mine) for my nano. I tried Googling this and found nothing. Mystified, I posted a pic of him on reefcentral.com <I would love to see this image, if you can grab me a link.  If it IS an Uca/fiddler, I might be able to get it closer to a species, for yah.  Not necessarily likely, but there are some great references on the web.> and still everyone was baffled. It was when I went to a different LFS that I realized what it is I and others are buying:  A female fiddler crab (my LFS who I thought was saying "fire crab" was actually saying "fiddler crab" but pronouncing it "FIDE-ler" and I misunderstood him).  Some LFS call them red crabs.  Again: orange, 1", walks sideways, black eyestalks, burrows in the sand. <Does indeed sound like a fiddler/Uca sp., as far as burrowing goes.> Mine has proven to be totally reef safe, hiding about 99.9% of her life. I've seen her for maybe a total of 60 seconds in 3 months! The females do not have the typical fiddler chelipeded and so look like something else. <Correct/agreed.> The problem with this is that fiddlers are supposed to be given a land/water environment, as they live in muddy mangrove patches and near the shoreline. Unfortunately, a few seem to find their way into the reef trade, and unwitting people like me and Sabrina wind up with them. <Mm, again, 'twasn't me....  "I just work here" <grin>.  Though I do have a couple fiddlers....  but mine are in a large sandy terrarium with a 2g saltwater swimmin' hole.  They seem to be doing quite well.> I'm sure she'd be happier in a terrarium, but she does just fine it seems in my nano reef. <If possible, you might consider setting up a land crab system.  You wouldn't believe how much fun they are.> Hope this helps! <Thank you very much for this!  And again, I'd love to see an image of your crab, if possible.> Alex <Wishing you and your firely FIDEler well,  -Sabrina>

Mystery Crab (Again) - 09/01/2005 Hi Sabrina! First off, sorry to you and Charlotte for confusing you! <Oh, no worries!> Here are two pics of my crab when he was in my 5g. Hope they help! <Mm, some, yes....  I still think this is an Uca (fiddler), and it *might* be Uca ecuadoriensis....  though I'm by no means certain.  A very cool little invert; thank you very much for letting us see the images!> Alex <Wishing you well,  -Sabrina><<Am moving this to the marine section, since fiddlers are marine....-SCF>>

Crustacean for a Community Tank - 05/21/2006 Hello folks, <Hello, Doug.> I've been reading your articles with interest but I still am unsure about what I should do with regard to finding a suitable crustacean for my community tank. <Someday we'll have a shrimp article up....  just (finally) wrote the thing.> This is a freshwater tank, 20 Gallons, 2+ years old, nice and stable. Right now I have 5 Rasbora tetras, 6 cardinal tetra's and one fairly large Chinese golden algae eater (5" long). We added the Cardinals a month or so back and they are doing fine. We wanted to get some kind of crustacean to complete our community but are not sure what would be best after reading about predation of tank mates. What do you think might work in this situation? <LOTS and LOTS of options....  Any shrimp from genera Atya, Atyopsis, Caridina, or Neocaridina....> I had thought of a Hammers cobalt blue lobster but after reading more about it realized that it would probably be the sole tank occupant in short order. <It would.  Stay away from any crayfish/"lobsters".  If you want something big and beefy, for a 20g tank, maybe look for Atyopsis moluccensis, the "bamboo" or "wood" shrimp.  A 20g tank is suitable for a male and a few females.  Or if you want something bright and tiny, look for "cherry" shrimp (Neocaridina denticulata sinensis v. red), "Rudolph"/"red-fronted" shrimp (Caridina gracilirostrus), or maybe "crystal red" shrimp, (Caridina sp.).  There are plenty of other small shrimp species that are less colorful, and most any would be of use here.  I do hope you are able to find a fun and pleasing pet to add!> Thanks for your advice.  -Doug <Glad to be of service!  Wishing you well,  -Sabrina>

Crabby Crab?  Sabrina Has Crab Envy! - 09/03/2005 Just bought an apparently Yellow Moon crab from the local garden centre.   <Research prior to purchase, next time....  I'm impressed, I suspect you have Geothelphusa albogilva.  This animal is currently unobtainable in the US.> Guy said it was ok in my tank with 3 goldfish which are very big.   <Likely untrue.> Got the heater for him and the right food etc.   <Goldfish are coldwater, shouldn't be heated.> He seems to want to get out of the tank all the time, life seems one big struggle to climb to the top and spend some quality time out of the water on top of the heater or filter system.   <Yup, this and all other crabs available in the freshwater hobby absolutely require a land mass with hiding space - these are land animals that spend some time in the water.  Geothelphusa albogilva is more terrestrial than anything.  At least the animal is actually freshwater.  I sure wish we got critters like that in the hobby in the US.> Can't find any info on these crabs <Not much out there, from a husbandry point of view - treat this like any other terrestrial semi-aquatic crab....  Give it a large land mass of several inches of sand and wood/leaf debris, with a great deal of cover/hiding and a few gallons of clean, circulating freshwater.> and worried I'm not looking after him right.  Can you give me any advice on making sure he has good quality of life?   <Just as above - this is an animal worth accommodating.> Would really appreciate your help and comments. <I'd absolutely LOVE some images of this animal.... please.... if you have time and a camera.  I have crab envy.> Kind regards,  Joanna <Wishing you and your new decapod well,  -Sabrina>

Crabby Crab?  Sabrina Has Crab Envy! - II - 09/07/2005 God I feel so naive.....just thought I was buying a funny cute looking crab to live next to my computer and look nice.  Guess I was major uninformed. <No worries....  The fact that you are seeking information is wonderful.> Didn't realize I had something unusual! Please excuse my ignorance. <Again, no worries.> I am a total animal lover and now dead worried this poor little creature is not getting the right life. I will transfer him to another tank and somehow arrange land for him to rest on and water when he needs it. How come I can easily buy him here and you can't over there? <I have never heard of Geothelphusa offered for sale anywhere....  But Europe and the UK always tend to get "new" critters a few years prior to the US.  There are many shrimp and crabs available in Europe that I'd do a great deal to get my hands on!  I suppose I shall just remain patient....> I will take some pictures of him and send them to you... <Much appreciated!  I would very much like to see if this is in fact the crab I think it is.> again excuse my ignorance as a first time crab owner but what's the interest? He's not yellow or looks like he's from the moon haha, just a small baby crab that's whitish in colour and likes sitting on the heater.   <Once in a proper environment, I suspect you'll find him much more interesting.  The interest, to me, is that I have quite a passion/fascination with invertebrates, especially crabs and shrimp....  the interest with Geothelphusa, to me, is that they don't or shouldn't require saltwater access....  If there were more truely freshwater land crabs available in the hobby, folks would be more easily able to care for them properly, which is one of my main desires....> Guess I'm entering a whole new dimension I didn't know existed out there.   <Invertebrates are really amazing animals!> Would love to chat more, thanks for replying so quick.   <You bet.  Sorry for the delay in this response; I've been traveling a bit.> Where about in the US are you?   <In California....  In the Santa Cruz mountains.  Beautiful place.> I'm over in UK in Yorkshire - God's Country. <Sounds excellent!> Best regards,  Joanna <Wishing you and your crabby pal well,  -Sabrina>

The Holy Soap Dish - 03/12/2004 My soap dish crab recently molted about, three weeks ago. <A Cardisoma species....  Perhaps Cardisoma armatum.> He has several holes, or sores, in his pinchers. He seems healthy, but I have not seen this before. Could this be a parasite or is there some deficiency in his diet? Do you know what this is and how I might treat it? <The likeliest thing that comes to mind is a deficiency in iodine.  Are you adding iodine to his water?  I use Kent marine iodine in my freshwater invert tanks, at a rate of ONE drop per TEN gallons, once every week.  I would imagine your crab could/would like to have that increased a bit, though.  The second thing that comes to mind, this species, as well as many/most other freshwater crabs, requires an area to get out of the water.  Without this, they may have health issues, perhaps including what you are describing.  If you don't have such an area, please do consider adding something for him.  Even dropping the water level a bit and adding a ramp/platform of cork bark in the back of the tank would do the trick.> I have had this crab for over a year now and want to keep the creature in good health. <Wonderful to hear.> Thank you,  Bob <Wishing you and your pinchy pal well,  -Sabrina>

Holy Soap Dish - II - 03/21/2004 Sabrina, <That's me!> I will take your advice. Many thanks for your help. There is not a lot of information about these crabs available. <Agreed.  I am SO glad you wrote back, I forgot to add the link I had wanted to give you.  Here's a listing of (mostly) freshwater crabs (also shrimp, crayfish, snails, clams....), auf Deutsch, but otherwise useful for identification - and if you can read it, or translate via Google's language tools, there's lots of valuable info there, too.  So, without further ado,: http://www.wirbellose.de/arten.html#Krabben > It was nice of you to share your expertise.  Regards,  Bob <Glad to have been of service.  Thanks for writing in!  -Sabrina> Legless Fiddler - 03/27/2004 Any idea how long it takes a fiddler crab to regrow its legs?   <A few to several molts, I would assume.> I have one that lost all but 1 leg and has his 2 pincers still (poor guy)   <Poor guy, indeed!  Yowch!> someone is obviously nipping at him, but haven't figured out who since I have so many other inverts.   <Yikes, that's no good.  He won't recover unless you separate him from whatever's hurting him.  He really needs a separate tank to allow him recovery time.  If you like, you can let us know what all you have in your tank, and how big the tank is, and we can try to figure out who the aggressor is.> Anyway, any idea how long till the poor guy gets his legs back?    <Feed him plenty, and be sure to add iodine to his tank, if you don't already.  This will help him as he molts to produce a good quality exoskeleton.> Thanks!  Jennifer Schelfhout,  Palatine, IL <You bet.  Wishing you and your crab well,  -Sabrina>

Killer Crabs - 03/27/2004 Hello, <Hi!  Sabrina here, today!> I am hoping that you can tell me if it would be possible for fresh water crabs to partially devour a human?   <Please envision a huge question mark floating about my head.  Er, *WHAT*?!?!> I am writing a screenplay in which such a horrible event would occur.   <Ah, good!  Whew!  At least you're not trying to account for a body in your back yard, heh!> I would like to confirm that such a thing would at the least be somewhat plausible. <Mm, I'm afraid not.  There aren't a great many species of freshwater crabs, for one, and all are pretty timid.  If the person were already dead, and starting to decay, I'm sure he'd be a tasty tidbit.  But a live, flailing person?  No, I'm afraid not.> I know that I have seen such things in movies involving sea crabs.  Pirates evidently used it as a type of torture to get people to tell them what they wanted to know.   <Even these scenarios are rather unbelievable, to me.> In my story, a villainous man bales out of a plane and lands in a large Mexican lake.   <Not even sure there *are* freshwater crabs in Mexico....  some shrimps of the genus Macrobrachium, yes, and these likely more aggressive than any crab!  But I still don't think they'd attack a person.  And somehow, being attacked by a swarm of hungry shrimp just doesn't have a very stunning quality to it ;) > He makes it to shore three quarters dead.  I need him to be disfigured in some way.  And this is what I have come up with!   What do you think?   <Um, how about drop him in drying pond, amidst a group of starving ten-foot alligator gar?  http://www.fishbase.org/Country/CountrySpeciesSummary.cfm?Country=Mexico&Genus=Atractosteus&Species=spatula  Or tropical gar?  http://www.fishbase.org/Country/CountrySpeciesSummary.cfm?Country=Mexico&Genus=Atractosteus&Species=tropicus  Fishbase reports these as gathering in large groups to spawn during the dry season - so, a large school of starving, sex-crazed gar?  Still a bit fantastical, but I suppose far likelier than man-eating-crabs.> Thanks for any and all help.   Martin Phillip <You bet - and thanks for sending us your extraordinary question!  Certainly brought a smile to me!  Wishing you and your screenplay well,  -Sabrina>

Killer Krabs - II - 04/05/2004 Thanks for responding! <You bet, Martin.> It's not the answer that I'd hoped for but I do appreciate the expert information.   <Flattery will get you anywhere :D > I really do not want to create an implausible scenario.  I'll think of something else. <Wish I had some better ideas for you, but good luck with your screenplay, either way.> Thanks again.  Martin Phillips <Any time.  Wishing you well,  -Sabrina>

Crab Attack - II, III - 04/09/2004  Sabrina -- thanks for your reply and suggestions.  <You bet - that's why we're here.>  As you asked, here's the scoop on my tank - 100 gal w/ about 65lbs live rock and live sand. Numerous "cleanup critters" -- 2 cleaner shrimp, 1 fire shrimp, 1 arrow crab (just got him, very, very small), 2 strawberry crabs, 3 emeralds, a variety of hermits from tiny blue legged, Mexicans, Scarlets, 2 peppermint shrimp, numerous snails too (obviously they're not the culprit) -- fish are as follows -- 1 blue tang, 1 yellow tang, 1 neon dotty back, 1 diamondback goby, 2 goldenhead sleeper gobies (mated pair), 2 Perc clowns (mated pair).  <My vote is on one of the Mithrax/emerald crabs, or one of the strawberries.>  You mentioned treating the tank with iodine -- is it safe for everyone else in there?  <Oh, goodness, YES! I had been given the original question, and answered, under the impression that we were talking about a "freshwater" (brackish) fiddler - I would *definitely* recommend dosing iodine for your inverts.>  If yes, I would appreciate dosage info.  <Please take a look at our Iodine FAQs: http://www.wetwebmedia.com/iodfaqs.htm and the various articles on supplementation and testing: http://www.wetwebmedia.com/marine/maintenance/index.htm >  THANKS SOOOOOOO MUCH!!!! Jennefer  <Any time.>  -----------------------------------  Sabrina -- I know this may sound totally nuts, but I'm thinking the culprit(s) may have been 2 (vicious) yellow tangs I got rid of (had 3).  <Er, yeah, multiple tangs in one tank is most often a pretty bad idea, especially of the same species. I've seen multiple yellow tangs slice each other to ribbons when housed together, even in large tanks.>  If I didn't see it for my own eyes, I wouldn't believe either that they actually went after my cleaner shrimps, ending up killing one of them, ripping half of the legs off the other one  <WOW.>  (he's much happier since getting rid of the 2 Satan tangs and growing his legs and antennae back and back to climbing on the rocks instead of cowering in a corner). I never saw them go after the fiddler, but I don't know. What do you think?  <Well, with the behaviour that you observed, I'm sure it's possible.>  I was (pleasantly) surprised to still see the fiddler crab even though he's just a body with 1 lonesome leg and his 2 nippers.  <Poor fellah! I'm glad he's holding on.>  It makes me sooooo sad every time I see poor "stumpy".  <Hah! I like that. 'Course, I have named a Sturisoma cat "Stick", and an L-260 Plec "Suckhead". Go figure ;)>  Anyway, would appreciate any and all suggestions.  <I would definitely test/dose iodine. Testing is a pain, but you get used to it.... or numb from it.... or something. Also look into calcium - er, and check out those links to find out more about what you can/should dose, and how to go about it.>  Oh, as far as treating with iodine, just to give you the full scoop on my tank, I have a wet/dry filter, w/skimmer and U.V light. THANKS AGAIN! Jennefer  <You're quite welcome. Wishing your crab a swift recovery, -Sabrina>

Mystery Crab - 04/06/2004  Hey guys  <Sabrina the freshwater crusty-freak here!>  I am trying to ID a crab that is appearing more and more frequently in Australian stores. It has been incorrectly identified by several stores as Amarinus lacustris (Freshwater spider crab). I suspect the supplier is keeping this myth alive *lol  <Yeah, frankly, I'm still confused on that subject. Here's the only photo/info I've been able to locate on the web about this poorly documented little beast: http://www.nzfreshwater.org/crustacea.html  (scroll down) and http://www.dlwc.nsw.gov.au/care/wetlands/facts/paa/plants/emergent.html  (scroll down to "Cotula coronopifolia - Waterbuttons").>  Anyway, the crab in question is often referred to as a "brown backed crab". Orange/brown body with a chocolate brown H symbol on its shell. claws of equal size and quite heavy set, not long/slender. It seems to get to about 2" shell width.  <Any chance you can snap a pic of this guy to aid in ID'ing him? The following two sources may help you: http://www.wirbellose.de/arten.html#Krabben and  http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabs.htm >  I would LOVE to know the scientific name for this little beauty,  <Me, too! I've looked through everything that I have to look through, but without a picture to go off, it's pretty tough to try to find a good ID. I would very much like to see what your fellah looks like!>  as although I am sure I could keep it happy using general crab knowledge, it would be nice to know its specifics.  <Agreed. Always best to know what your animals need - and crabs are pretty diverse.>  Sincerely, Abbey AKA Callatya  <Hope to hear back. -Sabrina>
FW crab from down under info. Hi, This isn't a question - I just happened across your website and noticed a question someone asked about Amarinus lacustris - a genuinely freshwater crab found in S.E. Australia.  Here is a photo if you are interested.  Its about 6-7mm across the carapace.  Although I am no expert, I'm happy to answer any queries anyone might have, although you were quite right in your reply - there is little info available.  It would be illegal to attempt to export this animal. <Thank you for this input. Will post on WWM. Bob Fenner>

Crab Questions - 04/15/2004  Hello Crew-  <Hello, Jessica!>  First of all, I wanted to tell you how much I've learned from your website on the subject of my newly purchased Sesarma bidens! However, I do have a couple of questions for you, and I know you can help.  <Whew, you're a lot more confidant than I am! But I'll try my best.>  I have a 10gal. freshwater tank for the two crabs I purchased close to two months ago. Both of the "girls", my 12 year-old son lovingly named "Tara" & "Melissa", have been doing wonderfully. They both have been eating well on a diet of algae pellets and shrimp pellets.  <So far, so good.>  But, after checking them both yesterday morning, and then later that afternoon, I discovered "Melissa" was in a normal up-right position, but wasn't moving at all. Maybe I'm being very ignorant and naive, but I didn't want to throw her out until I knew for sure that she wasn't actually dead and could be molting.  <No, I understand. Though, the molting process is usually relatively quick, and they'll usually hide while they molt, and while their new shell hardens.>  I did check her this morning and there's still no movement. I've spent the last three hours culling through information about the crabs, but I've had no luck in finding anything on what a dead crab will look like compared to a molting crab.  <At this point, if she's not moving, I would pretty much suspect the worst. I am very sorry. It may have been aggression from the other crab; this species, like quite a few others, are pretty aggressive with one another.>  We owned a very large hermit crab for five years, so I am very familiar with molting. But I've never owned crabs before.  <They're pretty much the same.... Though I would add iodine to the water (see our shrimp & invert FAQs for details), and would certainly allow them a space where they can get out onto a dry space somewhere in the aquarium; it is quite crucial that they have a land space.>  I also wanted to ask about the actual necessity for salt in the water for these crabs.  <It is unnecessary. They may do somewhat better in brackish water, and certainly need high-end brackish to breed, but should do quite well in freshwater.>  I found a ratio of 1tsp/10gal of kosher salt...it this a correct and safe figure to go with,  <Yes, certainly. You'll still be "fresh" water, essentially. Even salt-sensitive fish can tolerate this concentration.>  and will it hurt goldfish if I choose to put them in the water too?  <The salt would certainly be fine for the goldies - BUT - ten gallons is really far too small for goldfish. I would recommend something simpler in terms of maintenance; goldfish are really far too messy of waste producers to keep in such small confines. How about mollies? These would do exceptionally well, you could keep a few in a ten gallon with the crab, and bring up the salinity, even to full saltwater, if you desired.>  Thank you so much, and I hope to hear from you soon. Jessica Linaweaver  <You are quite welcome; thank you for writing in. Please let us know if you have any further questions! Wishing you and your crab well, -Sabrina>

Couple O' Freshwater Crab Questions - 05/02/2004 What is the condition in which the female crab will lay her eggs? <This is very, very dependent upon species; some will need brackish or marine conditions before they will mate, and a few species do not; temperature and pH may play a factor in meeting the animals' breeding needs.> Do the eggs have to separated from all other fish? <Crabs will carry their eggs in a sort of a trapdoor hinged pouch under their bellies.  The eggs should not be loose or separate from the female.  However, it would probably be a good idea to isolate a carrying female, to protect the eggs and hatching young from predation - from other crabs as well as the fish.  Wishing you well,  -Sabrina>

Molted Crab - 05/31/2004 I have a Red Claw Crab, he is my first crab and I don't know what to do now that he has molted. His old shell/skin is sitting at the bottom of my tank, I don't know if I should remove the skin or leave it in the tank. <I would leave it.><<Often are eaten, reincorporated into new exoskeletons... necessary mineral content. RMF>> I know Hermit crabs need their old skin to eat, but I don't know what to do with this one. <If it's not gone in a few days, pull it out.  I would assume the crab (or other denizens of the tank) will have made short work of it, by then, but if not, best to get it out.  Wishing you and your crab well,  -Sabrina> Shelly Warren Crabby Confusion - Playing With Common Names - 10/11/2004 I recently ran across a Red Thai Crab in my LFS.   <Hui.  With so little English information on crabs offered in the aquarium trade, I fear "Red Thai Crab" is just about as descriptive as "Small, colorful fish" to describe a neon tetra....  Not your fault at all, just the fact of the matter.> I have never seen one before.  It was huge and in fresh water, and obviously red.   <Well, red helps quite a bit.  Getting' some ideas, at least.> I have no idea what the scientific name might be, <Sad.  But not unexpected.  I haven't seen a single crab available for sale with a Latin name for a label.> and my search on the internet has proven well, let's just say made me hungry, I can now prepare crab 100 different ways. <Great!  You can come make dinner, then!  ;) > Now the meat of the email.   <The crabmeat, as it were.> I have a brackish water tank with a Snowflake eel, a dragon fish, and some Sailfin mollies.  I would like to add one of these crabs to the tank but......  I have no idea if it is truly a freshwater crab and more importantly will it eat my eel and dragon fish. <Well, let's try to explore *what* this crab is.  Also, a tank size would be of some assistance - also, I'd like to drop a bit of a hint that your eel may prefer saltwater as it matures.> Does it require a spot to get out of the water on occasion?  The size of the crab was a good 4 inches, could be bigger it was busy moving a large rock in the tank.   <Alrighty....  You say "obviously red", easily 4", and sounds like a bruiser to be redecorating his digs.  My first, best guess is Gecarcinus ruricola (possibly the genus name is spelled 'Gercacinus'....)  Please see here: http://www.wirbellose.de/arten.cgi?action=show&artNo=115 .  I have seen this species offered for sale quite a few times, now.  Some problems with this animal - and *especially* in keeping it in an aquarium - to my understanding, this crab, surprisingly, is not very aquatic.  In the wild, it rarely enters the water, and instead gets its moisture mostly from humidity in the air.  To keep it totally submerged is a short life sentence.  It should be kept in a terrarium with enough water available to be fully submerged should it choose to do so (for instance, low humidity).  The water available can be plain ol' freshwater, but I think it might be prudent to offer a separate container of brackish water, as well.  If I recall correctly, this crab gets big - roughly an eight inch leg span - and though not horrifically aggressive, I'm sure it would willingly pick off small fishes or land animals.  Feed with aquatic meats, also non-citrus fruits and veggies should be offered.  There is an Aqualog book by Uwe Werner available that has a (small) section on this crab.> My eel is about 18-19 inches long (of pure hunger) and the dragon fish is about 13 inches (odd fish there), neat how that fish eats. <Neat indeed!> Also I just bought a 150 gallon tank for my brackish system (have not changed it over from the 55 yet) Just how big will that Snowflake eel get? <Big.  Quite big.  I urge you to see here:   http://www.wetwebmedia.com/FWSubWebIndex/fwmorayeels.htm  and make use of http://www.fishbase.org as well.  As you will see, much is dependant upon specifically what fish you have.  Whatever your eel is, a 150 should be adequate; it's mostly just a matter of determining what kind of water it will need as it grows.> It was only like 5 inches long when I bought it and it just grows and grows and grows, oh and it eats and eats and eats, I love it. <Glad to hear it.  Amazing animals, aren't they?> Thanks you guys for any info you can give me. <Please do write back if you wish, especially if my guess on the crab in question was off - a very detailed description of color, placement and size of the eyes (widely spaced? long eyestalks?), whether one claw is significantly larger than the other, and any details you can muster will help.  And, of course, a picture is worth a thousand words!  Otherwise, you might be able to ID the feller here:  http://www.wirbellose.de/arten.html#Krabben .> Craig in Peoria ILL <Wishing you and your fantastic fishes well,  -Sabrina in Boulder Creek, CA>

A Sesarma By Any Other Name.... Would Be A Pseudosesarma 10/26/2004 Hi guys... <And gals.  Sabrina-the-freshwater-invert-freak at your service.> We need your help. <Well, what d'y'know, that's what we're here for!  Hope to help you out.> We have been getting conflicting information on our RCC. <For our readers, that's "Red Claw/ed Crab", or as you've mentioned in your subject line, Sesarma bidens....  Actually, this animal is now thought to be more accurately Pseudosesarma moeshi.  Just a fun tidbit.> One thing that everyone seems to agree on, is that RCCs are brilliant escape artists. <True.  Most (all?) crabs are.> However, when we have been trying to research as to whether they actually NEED to breathe air half of the answers are yes, the other half are no. <Mm, not so much that they need to "breathe" air (all land crabs use gills and require high humidity - even hermit crabs, which carry a bit of ocean in their shell!), but yes, they absolutely *require* a land mass to thrive.  They will not last long, forced to be fully submerged....  Or worse, fully submerged in a freshwater aquarium, as they are unfortunately sold to be.  In addition to their need to get out of the water, they also fare much better with some salt in the water.  Doesn't need to be much, but they do much better with a bit of salinity.> Could you please set the record straight for us? <Land mass required, yes.  Most definitely.  It will live for a time fully submerged, but will not thrive, and will not live long.> We don't want the little guy to die, but we don't want him to escape either. <Any chance you could drop the water level a few to several inches and offer a good-sized land mass (even a very large piece of floating wood) with lots of nooks and crannies to hide?  This would likely be sufficient.  I suspect that the reason they are so renowned for escaping is simply that they are desperate to find a way out of the *water*, not the *aquarium*.  All the same, a tight-fitting lid is definitely called for.  Do please try to accommodate this animal rather than returning him; you will be greatly rewarded with a fascinating pet, with just a little work.  Perhaps even a small, 10-gallon tank as a dedicated home for him and an opposite-gender pal?> Thanks so much, <You betcha.  I really hope you choose to make this work out - these are fun critters.> - Ian Fenn <Wishing you and your crab well, -Sabrina>

A Sesarma By Any Other Name.... II - 10/30/2004 Hello again, Gurus of Aquaria! <Well hello!> Thanks so much for your Red Clawed crab-help Sabrina. We finally found someone/place that knows what they are talking about! <Heh, or at least we *hope* we do!  So glad to have been of service.> We were wondering if we could please have some help with our cichlid tank now. <Whups, not me....  I am cichlid-ignorant, for the most part.  Chuck, our mega-awesome cichlid master is in possession of a duplicate email; hopefully he'll give you the answers that you seek.  I'll truncate this now, and give you a big hearty "Thanks!" for all the kind words.  Wishing you well,  -Sabrina>

Anomalous Crab Question - 10/30/2004 Hello, My little red crabs keep getting on the filter and just sit there like they are in a stream. <Er, do you know what kind of crabs these are?  Can you give me a good description of them?  Size, coloration, markings, anything like that?> I do not see how they are getting up there unless they can swim. Why and how do you think that they are doing this? <The how is the easy part.  Crabs are *amazing* for being able to climb nearly anything....  I wouldn't be too terribly shocked if they were simply climbing the glass!  But more likely, they're finding a way up to the filter intake tube, and climbing that.  Now, as for the "why" of it, there are likely a few reasons.  First, is this a fresh, brackish, or saltwater aquarium?  In what country do you live?  In the US, there are nearly - or absolutely - no crabs sold in the hobby that are truly freshwater animals.  Most will survive in freshwater for a time, but they will not thrive and will not live their full life span.  Moreover, nearly - or absolutely - no crabs sold in the trade in the US are truly aquatic.  All are amphibious, or land crabs that only occasionally venture into the water.  Chances are, your little inverts are just trying to find a way out of the water.  At the very, very least, I recommend you drop the water level a bit, and give them a surface to rest on out of the water.  Try to provide them with a few hidey-holes on the surface to help them feel secure.  Remember, crabs are extremely adept escape artists, and they can and will find any way out of the tank, especially if they're not happy with their setup.  Please be sure you have a tight-fitting lid, or you might wake up in the morning to find a crab cuddling you in bed!  ;) > Thank you Kayce <Wishing you well,  -Sabrina>

Got Crabs? Hi WWM Crew! I have a 20g FW tank. In that tank I have 4 guppies, 5 small goldfish (who will soon have there own tank), and 2 small catfish. I was wondering, can I put some small red crabs in there or will they harm my other fish. The ph is 7.2 and the temperature is consequence at 73* F. Will this cause a problem at all? Please, I would be very happy to hear from you. Thank you: ~Lena~ <Hi Lena, Don here. Sorry, can't recommend crabs. Although some will thrive in FW, most would do better in at least brackish conditions and all would need a place to get out once in a while. If they were to catch a fish they would kill and eat it. There are plenty of FW shrimp you could keep with the guppies and cats. BTW, You do need to move the goldfish and then increase the temp to 78> Thai devil Soapdish crab I know this is not truly an aquatic species, so I don't know if you  can help.  However, I thought that if you didn't know the answer, you may  know someone who does. <Mmm, am actually one of those "guilty" ex-retailers of yore who used to sell these w/o much knowledge of their husbandry> My friend has a Thai Devil crab (Soap dish crap).  His large  claw is inflamed at the joint where it attaches to his body.  He is in  a 10 gallon tank, partially filled with water.  He has land access and  spends most of his time there now.  He is still eating as normal and very  active.  The Ph of the water is 7.0, but she does not have any salt  added. <IS a freshwater animal, that DOES eat various meaty foods>   He is fed a varied diet of krill and hermit crab pellets.  She  soaks the krill in vitamins before she feeds them to him. <Good> I understand  that iodine is important to these crabs. <A essential micro-nutrient for much life, including you and I. I would add Lugol's solution, potassium iodide/iodate once a week or so... to this animals water.> Does he need special  lighting? <No> And could the inflammation be a sign of an impending molt?   <Maybe> He is full grown and they only molt once a year I think.  She is very concerned about his health, she has had him for about 6 months.  Any information would be greatly appreciated. Thanks, Caryn <I encourage you to place the above title words in your computer search tools and read what little there is posted on the Net re this crab/species. Bob Fenner> Fiddler Crabs, Ich Problems? Is there a safe medication to treat for ich that will not kill my fiddler crabs? <Yikes! Ryan here today.  We use a quarantine method to treat infected fish- That involves removing the infected animals, and treating them separately.  In that case, your crabs are safe!> It's been 20 years since I've had an aquarium, and it seems that many rules about keeping and caring for freshwater fish have changed.  <I'll say!> I did my homework and researched the subject so that I felt comfortable with my choices.  About 2 months ago I purchased a 55 gallon aquarium, and started with about 5 Neons to get the water cycle to do its thing.  I now have several fish: 5 swordtails, 6 mollies, 5 dwarf platies 6 dwarf Gouramis, a Pleco, 6 Cory catfish and 6 fiddler crabs.  (I love the fiddler crabs.) <That Pleco will soon outgrow the 55 gallon tank...I'd inquire early about trading him for a smaller Pleco once he's about 6 inches.> Everything was going well, including the birth of about 30 babies (black mollies, silver Lyretail mollies and sunset dwarf platies) until last weekend when I did a 25% water change to correct nitrate and total alkalinity levels.  I also rearranged the fake plants, rocks and log to allow the fish to have more swimming room and to ensure a better water flow from the filter.  I must have really stressed my poor fish.  The other day I noticed that 2 of my dwarf Gourami had small slits and little holes in their upper fins.  That evening I noticed my male silver Lyretail had trouble swimming and was at a 45 degree downward angle, and sometimes faced straight down.  I immediately added extra aquarium salt to the tank and increased the water temp to 82 degrees (from 78).  The following day, after work, I purchased a 6 gallon  'hospital tank', Maracyn and Maracyn-Two for my 3 sick fish.  Unfortunately, when I got home, one of the Gourami had died.  It looked to be sick for only 24 hours, so I was pretty shocked to find it dead that quickly.   I checked all my fish and decided that only 2 of the other Gourami had what is probably Fin and Tail Rot, so I put them, along with my male Molly into the hospital tank, using water from the 55 gallon tank.  (I didn't want to stress them further.)  I've been medicating them for 3 days now and they are looking much better.  My Molly is actually starting to swim somewhat normally, so I believe there is hope for him. <Sounds hopeful!> Now for the bad part... I came home from work today and found 3 more fish in the 55 gallon tank that look like they have Fin and Tail Rot.  It also looks like there may be a white spot or two on these same fish.  I have CopperSafe that I was going to use in the hospital tank if I needed to treat for Ich, but I can't use it in my 55 gallon tank as it would kill my crabs.  I've started treating the big tank for Fin and Tail Rot, but am not sure what to do about the possible ich, as I don't want to kill my crabs. <You're going to need to treat all infected fish in the QT tank.  Next time, add the fish to the display tank AFTER they have successfully completed 6 weeks of quarantine.  Then you won't have the same issues.  This time around, it's the long road my friend.  The answer to your question is no- There is no ICH treatment that is truly crab-safe.  Good luck, Ryan> Chris

Bettas and brackish This question is threefold, but background first. I have a two-year running planted tank with just about the easiest to grow plants in them (hornwort and Cabomba weeds) and a Betta (who is in heaven).  Ten gallons, inexpensive waterfall-type filtration turned all the way down to keep the water filtered but generally undisturbed at the surface, temperature at 82-84F, full spectrum lighting (as I pretty much used to use it as a plant-isolation tank to get the snails out of them... used to have a swarm of apple snails, which has since stabilized as the Betta tends to eat the egg sacs and young snails... basically anything he could fit in his mouth).  It was my first foray into plants and gave me the knowledge I needed to go into planting my goldfish tanks. <Outstanding> I am now interested in getting some (generally) bottom-dwelling small crabs, and according to the research I have done, while they can tolerate freshwater (poorly), they prefer brackish. <Most of the species sold in the trade, yes> I've done research into setting up a brackish system and I feel ready for it.  I've also been briefed in the requirements of the types of crabs I'm considering (but will eventually settle on a single pair of a single type, most likely the small red-clawed crabs) and feel ready to meet them. <Okay> Question one is:  Can the Betta tolerate a brackish or slightly-less-than-brackish salinity?   <Yes... as can the hornwort/Ceratophyllum... but the Cabomba may well do its falling apart act> I'd like to keep him (I got him as a fry and know he is around 19 months of age now) where he is, and possibly just slowly up the salinity to desired levels to get him used to it, as well as letting the microorganism population adapt to the change. <Good technique> Question two:  Would the Betta be socially compatible with these scavengers?  He generally will sleep on the plants and I've almost never seen him sleep on the gravel (I work nights, and keep the room dark on my nights off, so I have observed him during the 'night' part of his cycle). <The Betta should not harm the crabs, but the reverse may well not be so... almost all crabs are opportunistic omnivores... and if hungry, might attack, consume the Betta> Question three:  Answered on your brackish plants page, no, the plants will stick around. Thank you, Dan <Be chatting, Bob Fenner>

FW Crabs Hello again. Thanks for taking a look at my letter. I have a few more questions for you. Using the German crab ID page I found on your site, I have determined that my soap dish crab is the third Thai fresh water crab they have listed, it looks just like my little Carl, right down to the dark zig-zags on his appendages. It says it is of the Demanietta species, but that seems to include a lot of different looking crabs. How can I narrow it down further? < Do a Google search on the web using the Demanietta species you have already found. That should get you closer to a correct ID.> Anyways, I've started adding iodine to all my crab tanks. How often should I add the drop? daily? < Add the drop of iodine every time you change water.> The water I use is well-water with a softener. If this is no good, what type of water should I use? Would adding some sea shells add calcium to the water? < All crabs like brackish water. I would use the softened well water but add some sea salt and micronutrients at about 1/3 to 1/2 the dosage recommended for salt water.> I know the fiddlers prefer brackish water, does Carl need some salinity also? < You bet.> Should I change the water to brackish? < The sooner the better.> Would his feeder minnows tolerate the salt? < They are pretty tolerant to salt and would probably do OK.> He has not molted since I have had him, but I just figured he was big enough that he only molted once a year. Am I incorrect with this assumption? < Sounds like a pretty safe assumption.> How big is this guy supposed to get, anyway? What is this creatures lifespan? well, thanks in advance, Scott < They usually get about 2 to three inches across the body and will probably live between 2 and 5 years depending on how old Carl was when he was caught.-Chuck> 

Soapdish Crabs, Fiddlers, Ghost Shrimp hello: please, I was wondering if y'all could help me.  I have what was sold to me as a Soapdish crab in a 2' x1' 6" tank with about 4 or 5 inches of fresh water.  Carl, as he is called, has a 2" wide body and is probably about 6" across including legs.  he has relatively short (compared to my fiddler crabs) eye stalks and is a reddish brown color with orange legs and claws that have reddish brown "designs".   the tips of his claws are whitish gray.  he has easy land access but hardly ever comes out of the water.  is that weird? <Mmm, not necessarily>   he eats live minnows and frozen peas.  anything else I could feed him for a little more variety? <Other meaty foods>   please don't say crabs eat anything, he won't eat carrots or broccoli.   is it safe to feed him hot dog? <Mmm, no... too fatty>   he'll eat it and seems to like it but I took it away because I'm wondering if it could be harmful with all that sodium.  should I remove any left over fish parts from the water?   <Yes, I would> sometimes he just eats half a minnow and the other half  just floats around in the filter current.  will it muck up the water or make it unsafe for him in any way?    <Could. I'd remove all uneaten food> I have had him for probably 8 months and he seems to be doing well.   I just want to know if you guys and girls have any tips to make him happier and/or healthier.  I read something on your site about iodine supplementation for crustaceans? anything else? <You could monitor, adjust biomineral (mainly calcium) and alkalinity... has this animal molted while in your care?> what is krill, where do I get it and how do I "soak it in vitamins"? <Euphausiids... liquid vitamins... just putting a few drops on for ten, fifteen minutes before offering...> I love my soap dish crab(s) and would really appreciate any help y'all could give as there is virtually zip on the web about them. also, for anyone wondering, Carl (as with all Soapdish crabs, in my experience: I have 2 males, I lost a female when she wondered into Carl's territory) is extremely aggressive and will decimate anything it can catch, including other Soapdish crabs of equal or  greater size. does not play well with others. I've even heard of one wasting an Oscar. <Have seen this sort, level of "aggression"> oh, why might a fiddler crab in similar tank conditions up and die for no obvious reason. <Is a brackish water animal...> a not too old/big male that seemed to be thriving was fine one day and upside down dead by the filter the next. he shares the tank with 2 females and one other male which doesn't currently even have its large claw. I don't suspect foul play, I am afraid there is something wrong with the water or something. the tank has been in operation for at least 6 months and has a good filter. I've heard a terrible rumor about fiddler crabs just dying after a while in fresh (not brackish) water but I've had a lot of these wonderful, mostly peaceful crabs and this is a brand new occurrence. any thoughts?  might the same thing happen to Carl? <What is the make-up of your source water? You may have hard, alkaline water that "works" for both these species> just one more thing, I promise. I employ a multitude of ghost shrimp as janitors and I read on your website that it was easy to breed them. that is very exciting to me, please tell me more! I am so glad I found your website, I hope you can give me a few pointers. thanks, Scott <Use your computer search tool/s... much written on Ghost Shrimp. Bob Fenner>

Re: Soapdish crab hello again! Carl has molted! about a week after starting the iodine treatments, Carl (Thai freshwater- Soapdish crab) molted.  could this be directly related to the addition of iodine? <Yes> unfortunately,  it did not go well for the big guy and he lost a leg and his larger pincher. <Evidence of? Likely a lack of biomineral (calcium) and alkalinity... provided in foods, water...> the next couple days were very tough for both of us, as he just sat there and twitched and I was terrified that he wasn't going to make it.  the next day I came home from work to find him on his back and motionless.  I nearly lost my mind with grief until I noticed his mouth apparatus was moving. I very gently touched the tip of his claw and to my great relief he sprung to life, trying desperately to flip over.  the poor guy just didn't have the strength! he was still very soft, so I decided to let him be rather than possibly injuring him by flipping him over.  after a couple more days he eventually started to consume his exoskeleton and move around the tank.  Carl's gonna be ok!  whew! now for the questions: I've noticed that since the molt his carapace and claw look very strange- its a very dull tan-gray and none of his normal patterns, like the "H"  on his back, are visible. it just looks very worn, or something. I know crabs will sometimes come out of a molt a different color, but the way Carl's shell looks makes me think its related to his traumatic molt. any ideas? <Either lack of nutrition, water quality... or will develop color, pattern in time> Also, is it possible to over dose them on iodine? <Oh yes> should I add the drop only when I do a complete water change or anytime I replace water that has evaporated? <Best to do with (weekly) water change regimens> keep in mind I have a 10 gallon filter in about 4 gallons of water, does that make a difference as to how fast the iodine is getting used up? <Yes> One more thing: I really want to change my crab tanks to brackish but I have read that once crabs are in freshwater for so long, they cannot be switched to brackish. is this true? <Not so. Bob Fenner> thank you in advance. Scott

Injured Red Claw Crab Hi, firstly thanks for such a great website! The information here is comprehensive yet easy to understand. Unfortunately I have a problem with my Sesarma bidens crab. The other night whilst cleaning out the tank I did not notice the crab (Colin) burrowed under a plant, as he is almost always hiding under an ornament on the other side of the tank during the day (or breathing sitting out of the water on top of it).  He just recently molted (about a week ago) so I thought I would leave him under the rock and clean the tank around him. Well I dumped the plant in a bucket (with Colin underneath it) and proceeded to vacuum out the gravel and remove other ornaments to the bucket. It was only when putting the ornaments back that I noticed Colin at the bottom of the bucket on his back... I immediately picked him up and put him in the tank but he didn't move, I put lots of little bits of food in front of him and left him for the night thinking the worst.  When I came back in the morning he was on his back again but when I went to lift him out of the tank assuming he was dead he started moving his legs frantically, anyway I righted him but noticed that 5 of his legs were not working as well as one claw (I think they must have been broken in the accident) he was attempting to move around but the legs were preventing him, I left him for the day came back and he still had not moved despite attempting to with his working legs, so I amputated 3 of the legs at the base (not the claw) he is now a lot more mobile however he is unbalanced due to missing 2 back legs (resulting in him overturning and not being able to right himself frequently/a few times a day).  I have also since noticed that one side of his mouth is not working (i.e. the exterior movable parts of his mouth that he uses to clean his eyes) he can still move it a little but cannot properly function.  My question is: Is there anything I can do for Colin? I am aware that crabs can regenerate limbs during a molt but has he just sustained too much damage? <I hope not> My main concern is his mouth as I cannot see whether he is eating properly. Would it be kinder to just kill him now or try to aid his recovery?  <I would not euthanize this animal. It may well recover> It has been three days since the accident and he is still defending his food against the fish (a few platies) but I cannot establish if he is eating the food or whether the platies are eventually managing to take it all. In this situation could a premature molt occur or could he partially grow back before a molt? <Not before, but might molt again sooner, shrink in body size> I really don't want to have to kill him but equally I do not want to prolong his life if he is suffering with very little chance of recovery. He is in a 5 gallon tank with 0 ammonia, 0 nitrites, 20ppm nitrate, just over 1 tbsp. of salt per gallon and I am lifting him out of the tank daily for a few minutes to allow him access to air. pH is 6.6 (low I know but I added dolomite to the filter on the day of to raise it so hopefully that will start to take effect). Should I dose with Iodine? <Yes, I would> Sorry for the long question but I am very concerned about him.  Thanks, Chris <Do take care to maintain good, consistent water quality, assure this animal is getting food. Could take weeks to a few months, but may well be fine. Bob Fenner> 

Odd freshwater Crab behaviour I have a ten gallon tank with low water and rocks for crabs and other crustaceans. I bought some crabs and here's my q's. One: Are the crabs with one large and one small claw  males, and the ones with two small claws females? Two: Today the male??, one large one small claw, climbed out of the water onto the rock and started foaming? or bubbling from his face and doing something, like he was washing?? what is this? He the proceeded to sit then later he did this crazy claw dance, waving his arms around slowly in these rhythmic motions all the way out and then back in, what the heck? Does he have mad crab disease? Three: I put in feeder golds but they seem to ignore them. so I feed blood worms. should I add plants for veg food, or just stay with blood worms and whatnot? Four: The red crab I got has only one claw will his other grow back like at molting or something? Five: What's the ratio on crabs? The same as fish or? i tried here and all over to find good info on their behaviour and i came up empty handed! >> Yes, crabs with one larger claw are more likely males in most species. Crabs have to get oxygen when they are out of the water they will "chew" a small amount of water to mix it with air and get oxygen from this process, that is likely why your crab is foaming. He is waving his claws to show his territory and attract females, so he is not mad. You can feed with bloodworm, but try other foods to see what else your crabs will eat, it varies from one species to another, but most are omnivores. The missing claw should be replaced in the next molt,  I would not worry. For a great website on crabs and other crustaceans check http://www.crusta10.de not sure if it is all in English, but the site owner is one of the most knowledgeable people on the subject. Good Luck, Oliver Freshwater Invertebrates, ID? Hey guys I am trying to ID a crab that is appearing more and more frequently in Australian stores. It has been incorrectly identified by several stores as Amarinus lacustris (Freshwater spider crab). I suspect the supplier is keeping this myth alive *lol Anyway, the crab in question is often referred to as a "brown backed crab". Orange/brown body with a chocolate brown H symbol on its shell. claws of equal size and quite heavy set, not long/slender. It seems to get to about 2" shell width. I would LOVE to know the scientific name for this little beauty, as although I am sure I could keep it happy using general crab knowledge, it would be nice to know its specifics. Sincerely, Abbey AKA Callatya <Hey there, sorry it took me forever!  http://www.fishprofiles.net/files/~adam/tanks.htm  Right down the bottom of that page is a front-on view of that crab. I asked a large pet store and they said they are buying them under the name Holthuisana agassizi.  I cannot for the life of me find any reference to this species online, so I thought maybe, just maybe, you guys might have more references that I have access too. Thanks for your help! < I have seen this crab at wholesalers referred to as "red clawed crabs" from Asia. Try looking in the internet under that name to see if you can find more info. -Chuck>

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>



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