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FAQs about Marine Crabs 2

Related Articles: Crabs, Hermit Crabs

Related FAQs: Marine Crabs 1, Marine Crabs 3Marine Crabs 4, By Species/Group:  Arrow CrabsEmerald Green Crabs, Decorator Crabs/Sponge Crabs, Fiddler Crabs, Pom Pom Crabs, Sally Lightfoots, & FAQs on: Marine Crab Identification, Crab Behavior, Marine Crab Selection, Marine Crab Compatibility, Marine Crab Systems, Marine Crab Feeding, Marine Crab Reproduction, Marine Crab Disease, Emerald Green, Mithrax/Mithraculus Crabs, Micro-Crustaceans, Amphipods, Copepods, Mysids, Hermit Crabs, Shrimps, Cleaner Shrimps, Banded Coral Shrimp, Mantis Shrimp, Anemone Eating ShrimpCrustacean Identification, Crustacean Selection, Crustacean Behavior, Crustacean Compatibility, Crustacean Systems, Crustacean Feeding, Crustacean Disease, Crustacean Reproduction,

Mithrax sculptus, algae eater? Opportunistic omnivore? Both?

Hitchhiker Crab - remove 10/28/03 Anthony (or the nearest crew member), <yup> Have hitchhiker on Acro efflorescens. Crab of Mithrax configuration but furry (not hairy... ask my wife, er maybe not). <crab yes... Mithraculus, not even close unfortunately> Migrated to A cerealis. seems to be eating something (polyps?)? <quite possibly. Few if any crabs are reef safe. I trust none in my reef aquaria... crabs of all kinds are opportunistic predators as a rule> I removed to refugium but have other frags there. From the FAQs and such, I think he is not good for corals. <correct... a larger than normal risk> Am I on the right track or just paranoid? <valid concerns, my friend. In this case particularly because this crab is "hairy"... there seems to be some truth to the predatory inclinations of common hairy species versus bald and harmless Xanthid commensals> Regards Bryan <ciao, bub... Anthony>

Crab eating my Sally? Greetings. I have a strange fear:  <so do I... but I really don't believe that Tony Bennett Imitators are out to get me... I think?!> I have just noticed a small crab in my tank that might be responsible for my recent large Sally Lightfoot disappearances. <hmmm.... it's more likely that Tony Bennett killed your crab> This crab, whitish/grey in color is significantly smaller than either of my Sallies. One Sally went missing about one week ago, but I did NOT notice an ammonia spike and I attributed it to chance. I didn't worry until I noticed my second very large sally dead tonight with this crab within about 1 inch of it under a rock.  <Ahhh... an assassin sent by Tony Bennett> He was not eating the Sally, but it makes me wonder.  <sure... a dead corpse in ones lair is pretty indicative> Also of note is that my skunk shrimp's antennae are getting quite short (about 1 inch long),  <nervous tension... like nail biting> and there seem to be more and more empty shells (from snails or blue-legged hermit crabs?). <OK... in all seriousness, most crabs are opportunistic omnivores if not outright predators. Some behave for months but most will show their true colors in a year or two. Now or later... that crab needs to come out> Oh yeah, my tank: 90 gal, live rock, one regal tang, one Sailfin tang, one maroon clown. Assorted turbo snails, blue-legged crabs, red-legged crabs, sand sifting star, and the remains of two big sally Lightfoots. <yummy... crab legs. Wait while I go look for a tiny bib and a thimble full of butter> I have recently been putting in sea grape for my LFS for my tangs. I inspect the sea grape carefully for anything unusual, and then put it in my tank. The LFS keeps the sea grape in the same tank as its live rock it is curing. <wow is that dumb... a good way to wipe out their stock of Caulerpa or simply just give you a disease to take home for your fishes with the frequent turnover of fresh imports> I have noticed these same crabs on the live rock. The owners kill these crabs instantly when they notice them.  <remind me not to panhandle in their parking lot> They are not mantis shrimp, they look more like an emerald crab. The LFS says that they will eat corals, and generally do no good.  <they are simply omnivorous just like your sally lightfoot and a Mithrax. All are a potential risk in the long run. Tell him to keep the crabs for large fish tanks... they are great scavengers... or at least feed them to a fish> I am not positive that this hitchhiker got in on the sea grape, but it seems most reasonable. Also I have had these Sallies for 5-6 months with no problems. <OK> The lesson learned of course is NEVER put ANYTHING straight in the tank.  <BINGO> I knew this, but the LFS always claims they never have any problems . . . <Your LFS is pretty confident about a lot of stuff... remind me to send Arafat a memo to call your LFS> I religiously quarantine fish . . . I keep learning things the hard way. <alas... too many of us learn this way. Still, I'm grateful you do :)> Anyway: what is this nasty crab? How can I best rid my tank of him? Is this all just a huge coincidence? Thanks, John Michael Woodward <John... a tidbit we wrote on trapping crabs from our upcoming book on Reef Invertebrates:

"De-Selection": Removing Unwanted Crabs: Many folks discover resident crabs that seemingly appear from nowhere. Indeed, they arrive most often as hitchhikers on live rock or with other hard substrates including corals and other invertebrates. Aquarists are strongly encouraged to isolate all new rock and invertebrates (and fishes of course) in a proper quarantine tank where such crabs can be discovered, observed and removed if necessary. With proper quarantine protocol for all livestock, new imports are acclimated, addressed and evaluated with due process if not proper respect for their very lives. As responsible aquarists, we must also protect the our investment and the many lives of our animals in the full aquarium display from the introduction of a parasite, pest or disease. To place a new place of live rock or livestock into an aquarium without quarantine is literally playing a game of chance with the lives of your charges.  Proper quarantine is to last 4 weeks in a bare bottomed aquarium with 2 weeks being a bare minimum for reasonable assuredness of health. Live rock and any other new substrate (coral, shells, plants, etcetera) is to be propped off of the bare bottom of the QT (quarantine) vessel as if placed on a open rack. Improvisation with a plastic grid (like common "eggcrate" light diffuser material fro dropped ceilings) and short PVC legs makes a suitable table to perch a specimen on right quick enough.

Trapping in Quarantine... Baiting and trapping predatory crab species is simple enough. If an undesirable crab resides with the QT specimen, it will be easily attracted from high upon its perch to the bare bottom of the QT vessel with an enticing piece of meat (of marine origin). Reef keepers often use minced clam as bait fearing a predator likely to target Tridacnids. Truth be told, most predatory crabs are so indiscriminate that a leftover piece of ham sandwich would likely work as well! Trapping generally must be done in the dark of night, as many undesirable species are shy and nocturnal. Some species seem to be indifferent to the presence of red light and an incandescent, red-colored "party bulb" may remain lit over the QT aquarium for periodic inspection by the aquarist on nights when trapping is conducted. Most crabs are slow enough or unable to scale the smooth legs of the makeshift PVC rack easily upon discovery for the aquarist to net and remove the offender. For agile crabs, the bait may be tied in a satchel of nylon (aquarium netting bought for the purpose or a boiled piece of ladies nylon stocking). Predatory crustaceans like crabs and mantis shrimp (Stomatopods) often are snared easily in nylon netting; a small length of fishing line can be tied to the satchel of bait for extra security. Whenever possible, spare an unidentified or offending crab's life by remitting it to live in a fish-only or otherwise appropriate display or refugium; they can be quite useful scavengers. Otherwise, donate your trophy to a local aquarium store or aquarium society.

Trapping in Displays... Capturing predatory or nuisance crustaceans in a fully rockscaped display is sometimes not as difficult as it may seem at first. Crabs are especially clumsy and not so skittish about migrating to bait compared to Stomatopods. Using the above technique of a satchel of fragrant meat (silversides, clam, squid, and krill, for example), take the bait tethered by a long piece of nylon (clean fishing line or clear sewing thread) and gather a small to medium sized wide-mouthed glass jar. Pickle and mayonnaise jars work nicely for this purpose: smaller jars for smaller game may work fine. The wide-mouthed jar is to be buried almost entirely in the sand. If you prefer, the jar can usually be leaned against the rockscape just the same. The tethered bait, of course, is placed into the jar while you wait for the targeted scavenger to come out at night. Capture my simply be a simple matter of bursting with a diabolical laugh as you watch the trapped crab try to escape up the slippery glass walled prison of the sunken jar. Indeed, for most crabs it is easier to slide down into a glass jar after food than to climb back out with or without a meal. If necessary, the bait can be weighted in the jar instead and the nylon leash can be fashioned to pull a trap lid over the jar. There are many variations on this theme as you might imagine... be resourceful." Excerpted from Volume 1 of the Natural Marine Aquarium Series: Reef Invertebrates... info and pre-order: http://wetwebfotos.com/store/nma-ri.html Anthony Calfo, who... unlike Bob and Steve (thankfully :) ) is a dedicated student of American-style capitalism <VBG>. With kind regards, Anthony

Getting rid of unwanted Mithrax crabs Dear Everyone: I really have to congratulate one of your readers. Her suggestion of putting food in a tall slippery glass jar worked like crazy for me. I put a couple of oysters in a glass jar about 8" tall and surrounded it with live rock. In about 10 minutes, no longer, the crab showed up and tried twice to haul himself over the edge, which was slippery. I'll be darned if he didn't make it on the second try and he landed in no-crab's land along with the oysters. He is now out at sea via the flush system. Just had to pass this along to you as it was so easy. And to thank whoever suggested it in your crabby mail. Connie (still painting) <thank you for sharing! Anthony>

Crab Trap Hi Bob firstly I would like compliment you an a absolutely fantastic site both Wet Web and About. <<I would love to take the credit, but I'm not Bob, he's away diving. You've got JasonC here in his stead.>> I read as much as I can every single day and just can't seem to get enough information , this has to be the best hobby in the world !!! I recently took 3 or 4 small pieces of some real live rock from our ocean here in South Africa . Anyway It came with a really cute small crab at first I thought it was an emerald crab but as time went on and it started growing bigger and started turning browner. Yesterday I woke up and couldn't find 2 of my 2" Percula clowns. My question this must be the doing of this crab right?? <<Certainly a very good chance of it, yes.>> And I read a while back in one of your sites how to make a crab trap??? <<Not so much an article as perhaps an answer to a similar question in the FAQs - try here and beyond: http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabfaqs2.htm >> Please help . Thanking you very much, Werner Schoeman <<Cheers, J -- >>

Missing Cleaner Shrimp Hello again, Hope you are doing fine. I have a 29 gallon tank with 25 lbs of live rock. It has been set up for about 2 months. One of my white striped cleaner shrimp ( Lysmata amboinensis) has disappeared, I think overnight, a couple of days ago. There is no trace of him anywhere, no body parts or anything. The only other animals in the tank are another white striped shrimp, 2 peppermint shrimp, a small (size of a dime) emerald crab and some Cerith and Nassarius snails. <The Emerald crab is your most likely suspect from the list given.> Does this sound like there could be a mantis shrimp in the tank? <No> I have checked the tank at all times both day and night and never have seen a mantis. I even use a magnifying glass and flashlight and check all the holes in the rock, and have never seen a mantis. I was going to get a couple of captive bred seahorses in about a week, but should I hold off to be certain that I don't have a mantis lurking about? <I would remove the Mithrax crab.> Thanks again for all your help, Kevin <You are welcome. -Steven Pro>

Crab ID Hey guys, <cheers, mate> I a couple of photos of a crab which was a stowaway on some live rock I got about a year ago. He survived both the shipping and the curing process. In fact, I didn't see it for over three months but now he has molted 3 times and regularly makes appearances. However, I think he has been eating my snails???  <this crab like most is not only a possible candidate... but a likely one. They are opportunistic predators... leaning towards carnivores ;) > Is that possible?  <does a bear bring a Reader's digest into the woods?> Is there anything else I should worry about and can you tell from the picture what type of crab it might be? No ID from the blurry photo, but they are categorically omnivorous... few if any crabs belong in mixed invertebrate displays (reef tanks or not)> Thanks, Jeff J <best regards, Anthony>

Name that crab Hi Bob <<Hello - you got JasonC this time.>> I've got a couple of crabs that the local pet shop refers to as freshwater king crabs. <<I did some searching on the Internet using this moniker... didn't come up with much.>> They are reddish brown about an inch and a half across, flat with even sized claws with serrated backs. Any clues what they might be? <<Could they be... this crab? Sesarma bidens - the red clawed crab - here's a URL with some photos which may [if you and I are lucky] match up: http://wrongcrowd.com/aquaria/crab/  If that's not it, then I need to keep looking, let me know.>> Steve <<Cheers, J -- >>

Re: name that crab Hi Jason <<And hello to you.>> Thanks! but nope I got a couple of RCCs in there some fiddlers and a couple of burrowing Cray fish but these are about 3 times the size of the RCCs and much more flattened dorso ventrally. Any more clues I'd be glad to hear em <<Alright then... I'll keep looking.>> thanks again Steve <<Cheers, J -- >>

MYSTERY CRAB Bob, <Steven Pro this morning.> I have been enjoying your web site and the posted e-mails and thought you might be able to help me with a crab ID. I purchased 27 lbs of Fiji live rock a while back and made one of those amazing discoveries, I believe you called it the "Trojan crab." <Yes, very common.> After my hermit ate away a wall of algae I noticed this weird set of legs sticking out of one of the crevices. At first I thought one of my hermits went extravehicular on me so I accounted for the two I had. I was then trying to figure out how in the world a spider could get in my tank, since that was what the legs looked like and I could not see the carapace. Then it moved and pretty much ruled out the dead spider theory. Since then I have been able to get a better look at it and it is definitely a crab. The body color is sort of a grayish green, maybe a little mottled. The carapace is only about 1/2" (estimated), and it has two small equal sized pincers which I have seen used to eat algae. The legs seem to be the same grayish green, but with dark bands. An internet search led me to believe I might have a Mithrax here, but my local pet shop accurately pointed out that they hail from the Atlantic, not the Pacific (Fiji live rock), and that I likely had a stone crab. I have tried to find any reference to stone or rock crabs to no avail, other than restaurant listing....not much help there. Any ideas on what kind of a present I received? <I have no good guess on ID from your description. There are many, many crabs that come in as hitchhikers. You may want to try searching through several good books. The Baensch's Marine Atlas's are excellent.> Should I be worried and have it evicted? <If you have a sump, I would definitely remove and relocate it to there.> Thanks in advance for your help and I look forward to visiting your web site again. Sincerely, Mark <Have a nice weekend! -Steven Pro>

Emerald Crab Hello Bob, how are you today? <Bob should be doing wonderfully, he is diving in Cozumel. Anthony and I are holding down the proverbial fort for the week with Barb's help posting all our answers.> I bought a small emerald crab a couple weeks ago from the local fish store. He was missing one of his claws, due to a fight with one of the other crabs. They told me it would grow back quickly, <Back yes, but quickly no.> but after 2 weeks, I don't really notice anything growing yet (it is hard to tell, but there may be a stub starting to grow). I thought I'd ask you, since I know you all have lots of experience with marine life. Will the claw grow back, and about how long should it take? <Yes over the course of several molts. How often he grows and molts depends on your water quality and feeding.> Thanks much, Kevin D <You are welcome. -Steven Pro>

How many Emerald Crabs? Twofold question: Got rid of a bunch of Mithrax crabs. Kept two. What is "small"? How big do they have to get before we get them out of the tank.  <adult size approaches 6" diameter! I'd feel comfortable with a carapace under 2" regarding "fish-safe" crab size> I am left with one really small one but the other has awfully long legs and I worry about how long to keep him. His body is small but those legs! <forget the legs... its the pincers the fishes have to worry about!> #2 I have a 60 gallon reef tank with about 40# Fiji rock, 2+ inches mostly shells, etc.. Have a good skimmer and a Fluval pump that's supposed to be for 100 gallon tank. Tank is about 4.5 feet long. I have 4 clowns, 1 Gramma and 1 pygmy angel. They are all still juveniles, except maybe for the Gramma. Do I have room for a flame angel or anything at all.  <not likely with the other angel> Have always figured a flame angel would be the premier fish in my tank, but the one I got didn't survive shipment, so I got the pygmy instead. Would there be WWIII or is there just not enough room?  The size of the tank has nothing to do with it... a 1000 gallon tank is still only x feet long and too small for a flame's territory. It works on rare occasions but I would never recommend it> Long Question, but would really appreciate your opinion. The skimmer seems to be on under load. Thanks again. I guess you know from all the mail I've read that you are really, really appreciated by many, many of us. Connie Cavan <thank you kindly, Anthony>

Emerald crabs Good Morning Bob! Have a quick question for you. Would Emerald crabs eat Turbo snails? <Yes> I ask because I saw my large Emerald trying to pull at a Turbo last night. I managed to chase him away, the snail is ok. But now I wonder if maybe he is too big for my system now. Crab is app. 2 1/2 " across form one arm to the other, closed. I have a 75 gallon set up. Only 2 damsels, 2 Clarkii clowns, 1 cleaner wrasse, and 1 lawnmower blenny. Ass. hermit crabs, turbo snails, and 1 sand sifting starfish. <I would remove him.> Thank you for your time. Kat <You are welcome. -Steven Pro>

A Crab I Didn't Purchase Hello, I have a puzzling new addition to our tank. We have a 100 gallon Saltwater with about 150 Lbs live rock, corals and about 8 fish. <<Not really puzzling at all, quite likely a hitchhiker on the live rock - you do have a bunch after all. :-) >> Last week to our surprise there was a grayish white crab, about 1-1/2 in tall about 2" wide that came out from the lower rocks. It is the first time we saw him. When it moves it seems like an old man! We have red & blue legged hermit crabs and 1 emerald green algae crab but don't know about this one. Any questions about what it could be. <<Not really... it sounds like a crab to me. There are a silly number of crabs out there, and they are quite diverse. Some can really scoot, others take their time.>> I haven't been able to get it to come out at all. I have only seen it one other time since then. <<Try some food... crabs are quite opportunistic and will appreciate some free grub.>> Thanks for any info you can provide, Dave <<Enjoy. Cheers, J -- >>

Mithrax crab and Thalassia Seagrass questions Hi WWM Crew! Having just recently discovered your site, I want to tell you how much I have benefited from your answers. Thanks for sharing your expertise. Two quick questions: Will Mithrax crabs eat on a starfish? <Definitely one that is damaged or sick in some way. Less likely a healthy one, but still a possibility.> (My blue Linckia starfish appeared one morning missing an arm--and there are no other likely villains in the tank!) <Possible> Secondly, I am just about to start up a 15 gallon refugium as a part of a 75 gallon reef setup. I read with interest your recent answers indicating that turtle grass is superior to Caulerpa in a refugium. Any idea where I could obtain it? <Check the links page on www.WetWebMedia.com for livestock e-tailers. I know one of them carries it, I just forget which one.> Thanks in advance, Tim <You are welcome. -Steven Pro>

Crab identification Hi Bob, I just bought a piece of live rock. <<Hello, I'm not actually Bob... hope that's ok.>> After two days I noticed something moving in the live rock. On closer observation I saw a couple of small crabs about the size of a flat dog tick. They are light brown with dots on them. Do you have any idea what I have, and should I try to get rid of them. <<I'm not certain at all what type of crabs these are. If they really aren't any larger than a dog tick, I wouldn't be to concerned about them.>> Thanks, bluesky <<Cheers, J -- >>

Trapping crabs/DSB in Sump Hello there again, <<hello back...>> Thanks for the info on the Kole Tang eating habits question (re: eating fish poop). I feel relieved that it's OK for it to be doing this. My current question is on trapping unidentified crabs. I didn't take time to identify these crabs, but I have seen at least two light brown/tan colored crabs, with bristle-like/short hair covering most of their bodies. I want to trap them and move them to my 10 gallon for now, until I get a chance to trade them in at my LFS. I plan on getting some soft corals over the next year. I read about a fish trap consisting of an empty soda bottle with the tip cut off and the neck inverted into the body. Will this work for crabs too? <<I think so, yes.>> I haven't seen any DIY taps for crabs on the web, but I only went to two sites, suggested by the OZ's Reef website. If not, can you suggest a better way of trapping these suckers? <<Not really - crabs are suckers for stinky treats so you should have no difficulties with the soda bottle trap.>> Eventually, I'll remove the hermits, and replace with more snails. Also, I was thinking about putting 4 inches or so of aragonite sand into my sump after I take out the bio-balls to make a DSB and help reduce nitrates. Any thoughts? <<Create a plan that will perhaps allow you to run without the sump for 24 to 48 hours so that you don't cloud up the main system when adding the sand bed.>> Nitrates are currently <10 ppm, and I have about 55lbs of live rock in a 55 gallon tank. I would actually put it right under the box where the bio-balls are currently in and where the water drips down to, and use a separator to prevent sand from going into my main pump and skimmer pump. <<Hmm... that part sounds a little dodgy, only because you'd end up with a lot of sand in suspension - constantly stirred up by in the incoming water. You might want to re-think that part.>> Thanks a bunch, Randy M. Yniguez, MA <<Cheers, J -- >>

Mithrax crabs Dear Bob: First of all I have to tell you that your book is my bible. I keep it near my 60 gallon saltwater reef tank and as a result it looks pretty dog-eared. (It's had it share of salt water). I had a bad case of bubble algae and the fish store recommended Mithrax crabs. <Very typical.> My husband came home with one really full-sized crab and he couldn't do the job, so we got a bunch more, most of them small. I have four false Percula clowns, 1 pygmy angel and 1 royal Gramma, also a bunch of small crabs. I have a feeling I am missing some crabs, and now am frightened that I'll lose one of my clowns. They are all juveniles and one in particular is not a fast swimmer. The Mithrax crabs have done a good job but I now realize I have too many and would like to get rid of the largest ones and keep maybe one or two of the small ones. Question: How do I accomplish this without emptying out the tank. <I would try to trap they. Use the Google search engine on www.WetWebMedia.com looking for traps, mantis shrimp, etc. We have discussed several commercial and a few DIY traps.> Is it my fertile imagination that one night soon I'll lose a clown to one of these crabs? <No, a very real possibility.> And should I have any at all. <One to two small ones.> If I got a tang would that crowd my tank and would he eat the bubbles? <Depends on species, but probably yes and no respectively.> This is early Monday a.m. in California. I don't know where you are but I sure hope you check your email often. I think we need to take action within the next few days. PS We put some ROWAphos in our pump along with the carbon filters and it looks as if it's helping with the phosphate level, which was never sky-high as I have a protein skimmer and conscientious about cleaning the substrate. Thanks so much for your help. Connie Cavan <Good luck! -Steven Pro>

Crab & snail id help Hi everyone at WWM, <cheers, mate!> lets try again, hopefully without crashing your system.  <heehee...thank you :) > here are a couple of pictures of the hitchhikers I have. the actual snail is a light green in colour. the picture of the crab is very dark and is actually a tan colour. second picture is not quite as clear because of the plastic cage, but it shows his colour better. any ideas? do they both go or can they stay without damaging anything in my tank. Thanks Barry <it would be unfair to say that we (or most any aquarist) could ID these creatures down to the species level. Even genus for the crab if unlikely/impossible from the image. However... I can tell you that the are both likely omnivorous. In the case of the crab I am quite certain that it is likely unsafe with many invertebrates and small fishes. One of the "rules" with crabs is dark or black tipped claws and/or hairy carapaces mean trouble in reef tanks. I personally am not comfortable with most any crabs. By and large they are all opportunistic creatures. My advice is to pull both to a fishless refugium or remove altogether. Best regards, Anthony>
Swimming Crab Pics
Never found any ID on this little guy...he was SO cute.  He came in some maiden's hair algae & was the exact same color as it.  I just bought some more maiden's hair and have at 2 or 3 more in there...they're too shy to come out yet, though.  He only came out when the algae went sexual and died off.
He wasn't afraid of anything in the tank, including me.  Got some short vid of him swimming too...took some effort since he'd rather sit on my hand than actually swim!
<Interesting... and can use video. Bob F>
Let me know if you want video too.

Looking for key to Persian Decapods dear professor I'm study about fresh water crabs of Iran I need a key for identification pls help me faculty of science Tehran university Iran <Mmm, would have to research if there is such a reference in a college library. Not sure you're familiar with such bibliographic searches. Please see here re: http://www.wetwebmedia.com/litsrchart.htm  Do you have access to BIOSIS on the internet? The Zoological Record? I would start with their databases. Bob Fenner>

Stocking/id questions Hi WWM <cheers> question on stocking. I have a 50gal FOWLR, and a few polyps. presently I have 2 Percula clowns, a bicolor blenny, 2 peppermint shrimp, an emerald crab, various snails and hermits. I want to add 2 Firefish, a cleaner shrimp and a few more snails. do you see any problems with this?  <seems reasonable... some chance with Firefish aggression to each other> the Firefish will be mail ordered, should they be put into a quarantine tank, or just give them a fresh water dip to avoid the stress of moving from 1 tank to another?  <all fish should be quarantined without exception and Firefish really should be purchased locally if possible. They are notorious bad shippers> on another subject (thanks for your patience) I have finally caught my hitchhiker crab. attached is a picture. any idea what it is? is it safe or should I remove it? also attached is a picture of hitchhiker snail. looks like a whelk to me, should it be removed?? the actual snail is a light green colour. Thanks Barry <Barry and all WetWebMedia friends... please send any such pictures scaled down to a smaller 'Net sized image and never zipped (problems here). It absolutely crushes our mailbox with the amount of mail sent. Please resend my friend. Anthony>

Red crab is eating my xenia. Hi Bob, <Anthony Calfo in your service> I recently set up a 70 gal reef take to replace my existing 30 gal. I purchased about 50 lbs. of Fiji live rock from a local retailer which of course came with many pleasant surprises.  <yes...many such joys with fresh live rock> The tank has been running for about 5 months now. About 2 months ago I placed some green star polyps that are doing fantastic. Based on the success of the star polyps I figured I could start transplanting the rest of my corals into the new tank. I started with a small xenia and a Sarcophyton. This morning when I looked the xenia was gone and the Sarcophyton had a bite taken out of it. I looked with a flash light in the holes in the live rock and saw a red crab munching on the xenia.  <Arghhh> The crab is roughly the size and shape of an emerald crab but it' s bright red. Any idea what kind of crab this is and is it a notorious problem in reef systems.  <actually, most crabs including emerald crabs can be predatory in reefs. Most all are opportunistic predators. So... if hungry enough <G>> Other suspects are a 6 line and a peppermint shrimp. Any advice is appreciated. <the crab is by far the likely candidate. Do remove and resist even most "safe" crabs if you want great diversity of microorganisms in live rock and sand> Thanks John Allen <best regards, Anthony>

Sally Lightfoot Crabs Dear Bob: I too love your book and your site. It is very helpful for this relative newcomer. <Glad to hear it.> I have a modest 30 gallon reef tank running for 15 months. The inhabitants are limited: 1 true Percula clown, 1 Pseudochromis, 1 bubble coral, 1 carpet anemone, 40 lbs of live rock, and a clean-up crew - various snails and hermit crabs. Everyone seems fine. I fear I have made trouble for myself by mistakenly adding 3 sally lightfoot crabs today. I now realize that I should have only bought one according to what I have read. Since I bought them mail order, I have no return option. I can't see other local options. What is the likely outcome of keeping all 3? No trouble yet. <Your worst case scenario is one killing and eating the others. I would look into joining a local marine society. The education one can receive is great, but you have the added benefit of other hobbyists with other tanks to take a creature off of your hands or for trading. Thanks, John Rowley <You are welcome. -Steven Pro>

Problems Shedding, Crab Hi, How are you today? <Very well. Just got DSL and I am flying about at high speed.> I have a quick question.....I have a Sally Lightfoot that seems to have completely shed, but she lost two of her legs. Is this normal, and will she be okay? <Normal to shed, but not normal to loose appendages in the process. They will grow back, but maybe a sign of a lack in certain necessary elements; calcium, carbonate, iodine, etc.> Thank you for any info. you may have. Marci <Test for what you can and take any corrective measures needed. A good water change is the easiest way of fixing any potential water chemistry imbalances. -Steven Pro>

Questions about Salt Water Crabs Hi Bob, <<Not Bob, actually but JasonC filling in while Bob is away Diving.>> From many of the postings on your site it sounds as though stow-away crabs are problematic for many. <<true, true>> I have a different situation in that a small crab we caught last summer off cap cod (I think it is a decorator, but am not sure) <<decorators are funny crabs>> has become the focal point of may daughter's small 8 gallon tank. For many months it was very active in the tank especially when there was food involved (like the times he ate a clam, two snails and a couple hermit crabs). However, for the last few weeks it has resigned itself to remaining buried in the sand and rarely comes out (even during feeding time). He molted once, about a month earlier, and had a similar behavior, but it did not last as long. Is it normal for SW crabs to act sedentary prior to molting? Should it take several weeks? Any suggestions would be appreciated, my daughter is quite attached to the little guy (and I must admit, so am I)..... <<Oh boy... action packed. Well, I actually don't have a lot of experience with crabs, and just on the quick description it does sound like some kind of molting event. Again, because I don't know crabs well, I can only talk about crustaceans I do have experience with, shrimp and lobsters - which really aren't that distant cousins. Two things come to mind about molting - first is cover. Do you have plenty of cover/caves for your crab or does it prefer to bury itself? Right after molting, the beastie is very vulnerable, shell is soft, and so they need somewhere like a cave where they can back in and hopefully scare people away with the claws while they harden back up. Next thing, and this is related is that the molting is chemically affected all through the process. Many people tie iodine/dide to successful molting events, but I've got no data on this. Either way, I would ask you what your water changing/augmenting habits are on this tank? It could also, come to think about it be a hot/cold thing - crab may not like tropical conditions. Just theories, really and no sure way to tell. Here's some links on the WetWebMedia site that may help: SW Crabs: http://www.wetwebmedia.com/swcrabs.htm  FAQs on SW Crabs: http://www.wetwebmedia.com/swcrabfaqs.htm >> Thanks, John Fijol <<You are quite welcome. Cheers, J -- >>

Staghorn Crab Hello, I have had my Staghorn crab for 2 months now and the coral on its back is beginning to turn brown (it was all a sandy color.) <Usually a sign of inadequate lighting. The coral maybe able to adapt to the lower light source or it may suffer from a daily small loss to finally succumb months later.> I realize that the coral is living... could it just be algae growth on the coral or is it dying? <Hard to say with the info given.> I have to say that as a beginning marine aquarist, your book has been my Bible. <Agreed, Bob's book performs an incredible service to the hobby/industry.> Many thanks for your help! Susan <On a separate note, I got a virus warning with your message. You may want to have your computer checked out. -Steven Pro>

Crabs eating fish <I agree that it is possible, but I am just passing along what is likely. We will always have exceptions with animals in aquaria when some individuals don't read the same books we do to know how they should behave <wink> like Sally Lightfoot crabs eating small fish or Purple tangs eating coral. Indeed we can find tens or hundreds of people with such a bad experience. But there are many thousands of people that enjoy such creatures behaving in a more agreeable and expected manner. It is based on this that we share such advice as I think you have alluded to at the end of your message. In a manner of speaking, these crabs are so good at eating microalgae that if over 90% are reef safe (and say up to 10% are not to some degree), then it serves the greater good to make a generalization about the species in captivity. But thank you for speaking up and sharing your input! kindly, Anthony> Hey Anthony, I just read this post and you said this before. I have witnessed this myself. I am very sure the fish was healthy. > I just moved 2 emeralds and a sally lightfoot out of my tank due to fear of > them eating fish. Would they be able to hold their own in my other tank, > which I will be adding a peacock mantis shrimp to soon? Of course I am sure the mantis would eat the crabs!! >> <that is pretty crazy on both counts, my friend (especially for the >> sally)... the crabs are unlikely to harass any HEALTHY fish, and they are > >unlikely to survive with a mantis. Anthony> >ok if you think so. I have just heard others accounts of sally Lightfoots and >Emerald Crabs eating like one inch clowns.  Maybe he read one of my one or two posts :-) on WetWebFotos, but this did happen to me. I am very sure the clown was healthy. He was about an inch long, and the Sally light foot was very big. The clowns had been in Qt for about a month. There was no sign of illness whatsoever. I took the fish away from the crab but though it was still alive it didn't live much longer. It was swimming and then it got caught-- just like that. The thing is that crabs are excellent for control of hair algae and so forth- so. I am not sure what I will do on my next tank set up. --des/Jane

Crabs with Mantis I just moved 2 emeralds and a sally lightfoot out of my tank due to fear of them eating fish. Would they be able to hold their own in my other tank, which I will be adding a peacock mantis shrimp to soon? <that is pretty crazy on both counts, my friend (especially for the sally)... the crabs are unlikely to harass any HEALTHY fish, and they are unlikely to survive with a mantis. Anthony>

Re: Crabs with Mantis > I just moved 2 emeralds and a sally lightfoot out of my tank due to fear of > them eating fish. Would they be able to hold their own in my other tank, > which I will be adding a peacock mantis shrimp to soon? > <that is pretty crazy on both counts, my friend (especially for the > sally)... the crabs are unlikely to harass any HEALTHY fish, and they are > unlikely to survive with a mantis. Anthony> ok if you think so. I have just heard others accounts of sally Lightfoots and Emerald Crabs eating like one inch clowns. Based on your response, I guess I will put the sally and emerald back in. Thanks <really just a judgment call but do resist from moving any creatures repeatedly in such a short time... some hardy creatures can die that way. Technically anything that comes from a reef is not reef safe. Everything on a reef must eat something else on a reef (no take-out food, eh?). It then is a simple matter of if we find their "dinner" desirable or not that skews our perception of reef suitability. We have all heard stories of some dwarf angels and Zebrasoma tangs eating coral while other of the same species do not. Our captive reef denizens unfortunately do not read the same books that we do <smile>. Just weigh your options... do you need the algae control more than you fear their risk to small fishes? I think it is fairly safe. At least as small fishes go, they are safer from crabs than they are from Yellow and Sailfin tangs... hehe. Mean little bugger sometimes! Anthony>

Snails and Crabs die! Dear Bob: I'm forwarding this question to you, hoping you can help out this army guy! Howard. <Okay. Oh, see Steve answered. Bob F.> <Steven Pro this afternoon. I have a few suggestions. Yes, there are commercially available copper test kits, but your fish would be affected to high levels of copper too. Any detectable level of nitrite is bad and needs to be addressed. I would also look at his acclimation procedure. Many people kill a lot of inverts by exposing them to large shifts in salinity. Float the bag for 10 minutes, add one cup of water, float for 10 minutes, add one cup of water, etc. until temperature and salinity match. -Steven Pro>

Re: Alright, who did it? (marine tank pests) Hey [again], <whassuuuup? Anthony> I have a 25 gal. reef tank -- all the essentials. I've had it for about a month. A week ago I got my first inverts. All levels in check. Salinity in check. 5 red hermits, 5 blue hermits, 3 bumble bee snails, 10 snails, 1 sally lightfoot, 1 emerald crab, 2 starfish (one brittle and one harlequin), 2 elephant ear corals  <these Corallimorphs grow enormous and are predatory on fish!!! you've been warned <smile>> that came with the live rock. Over the past month the Coral Vital has really brought back the color to the corals.  <careful not to be too heavy handed with this or any nutrient in such a young tank. Its a good way to grow nuisance algae!> The center is now fluorescent green with the surrounding flesh purple. Well, this morning I woke up and there was a red hermit crab half eaten on the sand bed. Also, one the corals was destroyed (whatever ate it didn't leave much!). I have noticed the snails near the corals but I don't think they could knock it over. So, my question is .... was it one of the "known" tank members,  <a rogue species of hermit may have slipped into the blue or red leg species group (wearing the same shell)... look for brown or green legs> or could it have been something else? I saw a bristle worm about a half inch long on the tank wall the other day but couldn't get it. < a very minor concern and actually beneficial when small> But, at this size, I don't think it could have done any damage. I don't hear any clicking at night so I don't fear a mantis shrimp, but I am confused. What would have eaten the red hermit? Any advice obviously would be great. Thanks for everything. < do examine all of the hermits first... a rogue species is common. Else, bait the tank at night with a tall glass jar leaning against the rockwork with meaty food at the bottom. The premise is that a predatory crab if any will scurry down but not up glass easily> Ari <kindly, Anthony>

Re: Alright, who did it? (the Butler crab) AH-HA!!!! I found it! You were right (go figure).  <yes...even a blind squirrel finds a nut sometimes. Anthony <G>> This morning one the hermit crabs hitched a ride on the back of one of the snails. The snail was about 3/4 up the tank wall when I took a better look at the crab which occupied the shell that I thought was red hermit and it was brown with a big left claw.  <yes...common to see predatory/omnivorous stowaways in "safe" species shells> He's not "with" us anymore.  <where did he go? Did he get traded to another team? Must have been Pittsburgh Baseball team management... as soon as we get a lively one...Bam, gone!> So, today I have two questions -- 1) did this rogue crab come with the live rock? It must have b/c there are remains of the red hermit that it killed ... and I didn't buy any crabs w/out shells. <are your really that certain that it wasn't in the original purchase unnoticed and believed to be a red leg? That's most common. simply overlooked> 2) last night I brought home a Pseudochromis (strawberry) and a six line wrasse. I have a 25 gal. reef system. The Pseudochromis took immediately to the tank (I acclimated both properly). The wrasse was hanging out by the power head while I watched. Then I fell asleep. This morning they were both in hiding (I think). I saw the Pseudochromis stick his head out of some crevices/tunnels and swim back and forth. I cannot for the life of me find the wrasse.  <wrasses commonly hide for days (some weeks then reappear)...many in the sand! Don't give up just yet> I have the rocks set up so that there are *plenty* of hiding spots, many of which I cannot see from any angle, but should it be out and swimming about or is it just going to take a few days to get used to its new home. And also I'm feeding them both frozen seaweed -- is there anything else that they would like to eat? Thanks for all your assistance. Ari <the seaweed is fine for omnivorous/herbivorous fish... but they are not. They both eat meaty plankton... you will be better off feeding a mixed meaty frozen food, some Sweetwater plankton (to be refrigerated), frozen Pacifica plankton and Mysid shrimp (never brine). Kindly, Anthony>

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