Please visit our Sponsors
FAQs about Marine Crab Compatibility, Removal Strategies... 2

Related Articles: Crabs, Hermit Crabs

Related FAQs: Marine Crab Compatibility 1, Marine Crab Compatibility 3, Marine Crabs 1, Marine Crabs 2, Marine Crabs 3Marine Crabs 4, Marine Crab Identification, Marine Crab Selection, Marine Crab Systems, Marine Crab Feeding, Marine Crab Reproduction, Marine Crab DiseaseMicro-Crustaceans, Amphipods, Copepods, Mysids, Hermit Crabs, Shrimps, Cleaner Shrimps, Banded Coral Shrimp, Mantis Shrimp, Anemone Eating Shrimp Crustacean Identification, Crustacean Selection, Crustacean Behavior, Crustacean Compatibility, Crustacean Systems, Crustacean Feeding, Crustacean Disease, Crustacean Reproduction,

Compatibility/Decorator Crab   03/9/06 Hello WetWebMedia crew, <Hello MR.> We have a 55 gallon tank with 2 tangs (yellow and a 2 inch blue one), 2 damsels, 1 clown, 1 cleaner shrimp, 7 small hermit crabs, 2 anemones, and 1 black cucumber.  (We are going to upgrade to a 90 gallon tank in the summer. ) We recently purchased a decorator crab and are wondering if they are compatible with cucumbers and cleaner shrimp.  The crab is a nice little addition to our tank and he's quite a colorful character.  Our cucumber is quite the explorer,  he likes to go everywhere in the thank and sometimes right next to the decorator crab.  However, I am worried that the crab may hurt the cucumber one of these days, which will cause him to nuke the tank.   As a precaution, we took the crab out and placed him in our quarantine 10 gallon tank until we know he is actually safe.   Could you please email me back at this address with your answer?  <They are not reef safe and by your email I'm assuming it is a fish only tank.  Their activity of placing pieces of sponge, algae, polyps, etc on their back (carapace) will cause some damage to these animals and renders them not reef safe.  Other than that, should be safe with what you have now.> Thank you so much,<You're welcome. James (Salty Dog)> MR

Re: Decorator Crab Compatibility  - 03/09/2006 Thank you for the prompt response James. :) <You're welcome.>  Also, I forgot to mention our little incident we had a couple of days ago.  We had 2 clown fish in our tank.  (One of them was looking sickly).  He was still alive when we went to bed, but when we woke up the decorator crab was eating him.  I was wondering if the crab could have caught him and killed him?  I have heard that they kill small fish when they are sleeping.  Is this true?  <Small specimens shouldn't attack fish.  I'm guessing the fish died and the crab came to supper.  James (Salty Dog)>

Atergatis floridus (Hitler Crab)   03/07/06 Hello again, <Sieg heil!>             I have a hitchhiker crab in my Indonesian rock that I have identified from pictures as Atergatis floridus. I did a search on the web and found that its flesh is poisonous if eaten. My wife thinks it killed our cute little Red Scooter Blenny (Synchiropus stellatus) <Not surprisingly> that we had in the tank and has named the crab 'Hitler" accordingly.  It was not to be found one morning and she is convinced that "Hitler" is to blame. <Mmm> I now think there is a good possibility that this is what happened as well. The Dragonet was doing well for several weeks gorging himself on the plethora of "Bugs" that inhabit the tank as would any Dragonet. We really miss watching him hop from rock to rock picking at bugs. They really are cute little guys. Anyway I have been unable to find out if it might eat any of the corals <Das ist verboten! But might> I have in the tank which is a LPS Lagoon type tank with a lone Purple Firefish currently being the only vertebrate. <...> The Cnidarians are various Euphyllids, Brains and Goniopora. He is surprisingly strong for his size and has pushed some of the corals (Elegance, Goniopora) around on the sandy bottom where they have been placed. Last night I saw him overturn a large Goniopora once while digging underneath it (probably was digging for worms I would think). <Or what have you> I'm beginning to think my better half is correct in telling me I need to give Hitler the ol Jack Boot in the posterior before it really does some damage. <Javul, I would> I'm thinking I could try putting some krill in a large fishnet and hopefully he will go for it and I can lift him out. He is pretty fast and very cautious so it won't be easy to catch him. <I have faith in you Colonel> I have a ten gallon in the basement where I put my Sargassum, Chaetomorpha and other algae trimmings and I was thinking I could put Hitler in there where he can't hurt anything. <Worth trying> I really don't want to kill it even thought my wife has already given Hitler the death sentence. Thank you, Bryan D. Gatewood <Good hunting. Bob Fenner/Klink>

Crab Compatibility?   2/7/06 Hello WWM: <Frank> You have been instrumental so far in the health and upkeep of my tank and I'm hoping to take advantage of your services one more time.  I have had a decorator crab for about 2 months, I think its great and one of the most interesting members of my little community.  As an invert fanatic, I was also interested in the Hawaiian Strawberry Crab (the site does not provide the scientific name so here is a link to the site if it helps http://www.saltwaterfish.com/site_11_03/product_info.php?products_id=415&parent_category=4&category search=63&root_parent_id=4). I know that crabs especially tend to be creatures of opportunity and was wondering how likely these two would be to attack one another. Sincerely, Frank <Mmm, looks like Liomera rugata... a Xanthid... is opportunistic, though small... will "pick" if hungry, there's opportunities. Bob Fenner>  

Can you find the crab?

Decorator Crab  12/5/05 Dear WWM, <Hello Frank. Were not very 'dear' here at WWM at all, in fact some of us are a bit 'disturbed,' ahem, but that's a story for another time.> Again, thanks for all the help and information you and everyone else has provided me. <I'm glad you have found us useful.> Yesterday I bought a decorator crab. <Okay.> Despite the fact that so far he has only attached a few pieces of crushed coral to himself (herself) and one tiny polyp, I am fascinated by this little guy and was wondering if more than one could co-exist in a 55 gal tank? <Due to their potential size and potential very predatory nature I would not.> Also, I've been reading up on them on your site, but was wondering if there was anything particular I should know (be warned) about. <Yes the above that they can become quite aggressive/territorial/opportunistic with age and size, especially on smaller invertebrates and as you know their 'job' is to 'borrow' pieces of sessile invertebrates, at times they can also damage the animal in this action.> I attached a picture incase there is a species issue and just because I wanted to show him off. Sincerely, Frank <Adam J'¦who will remember not to delete the picture this time> <<Good job, Adam!  Now, I just need everyone to remember.  Marina>>

Here's her crab, missing one of this anemones.

Pom Pom Crab - Lybia tesselata 11/24/2005 Great site, guys.  <Thank you Steve> I've searched the site as well as the web and have been unable to find an answer to my question. What type of anemone does the Lybia tesselata crab carry?  <The Pom Pom Crab will normally arm himself with anemones of the Bunodeopsis species (Beaded Anemone). Shouldn't be too hard to find as San Diego declared them a pest as swimmers were complaining of being stung by them in Mission Bay.  They are not native to Mission Bay, just got there someway.>   <<Likely got there the same way Batiguitos Lagoon got its Caulerpa taxifolia.  MH>> My friend's crab has lost one of his.  <James (Salty Dog)> Thanks a lot. Steve Wright

Re: Random Mithrax crab death or mating? - The mystery Thickens Like Gumbo  11/11/05 So the mystery thickens.  As I deal with another bout of insomnia I decided to use my time productively on my tank. <Oooh, good start...> I set out my mantis trap.  And in doing so decided to feed the tank a little at night and watch.  Well, I saw all sorts of new worms (red and black bristle from 1-4  inches, an earthworm" that was 6 inches, took him out, and some brown worm that looked like the biggest pod ever who popped four inches out of a hole and pulled a freeze dried shrimp down the hole with him in the blink of an eye!). <Yowzah!> So here is the mystery.  As I said I had 2 Mithrax crabs.  Guess what.  I still do!  When the worm that grabbed the freeze dried shrimp had it part of the way down the whole, a claw comes out and grabs the shrimp!   <Ahh, those molting so and so's> Well because I had be watching, I did a little searching and found that I still had 2 crabs!  So where did the 3rd now dead one come in from? <Just the shells, man?> I thought back and realized that the crab that died looked a little funny.  He was hairy, and really more red and white/gray stripped.  He also seemed a little smaller then my Mithrax.  So the mystery deepens.   I had a random crab who must have been small enough to hide somewhere on my rock during the 8 week curing process and stayed out of sight until today when he died!  I have only added 1 piece of rock since, a rock with my xenia on it.  Except the rock has no crevice big enough for a crab of that size to fit in. So this is more of an update then anything else.  I love this hobby!  Thanks for helping me so much in the past. Now I have a new obsession, worms (and catching that mantis shrimp, the popping is driving me bonkers)! <Might be an Alpheid...>  I have some unidentified worm I have to send you a photo of.  Looks like a meaty version of a feather duster, has been on board since I got the rock, has never moved or grown, but today happened to grab a krill out of my tongs and eat the whole thing, which was the size of his entire exposed mouth! Thanks again. Marc <Thanks for the update! Bob Fenner>

Concerns Regarding a Hitchhiker Crab 10/16/05 Hi There, <Hey, Mike G with you this evening, glad to see the rain has finally cleared up> Firstly thank you for answering my previous email/post about Clown Eggs.  Now we have another Drama.. <Such is the nature of the hobby.> We brought some live rock today and added it to our Clown tank. We also have a 20cm Radianthus Anemone. A crab has appeared in the tank, it must have hitched a ride on the live rock from the fish shop!! <Likely.> The crab is dark but has striped legs. We noticed the anemone kept shuddering while the clowns were swimming around it, so we had a close look then we first noticed/saw the crab crawl out from near where the anemone was wedged between two rocks. We are concerned that this crab may have been or will pinch the anemone, or damage it in some way. The crab is small 2cm. <Identifying crabs is a difficult thing to do WITH pictures, without them I'd not hazard a guess.> But we realize crabs and anemones both live in the sea so they may get along ok?  <Great White Sharks and, say, damselfish live in the sea, and they don't really get along alright.> Should we leave the crab in the tank or take it out? <I'd remove it, just to be on the safe side. If you'd like an ID, get a picture and try asking DR. Ron Shimek on www.rshimek.com or, if you have ReefCentral Account, his forum is good for such cases. He tends to be very, very good at invertebrate ID.> The crab obviously has its hiding spot right where the anemone is wedged between two rocks so to get the crab out will be hard cause we will have to pull these rocks apart, but the anemone is stuck to both of them. What do we do?  <Hmmm... Bait a trap?> Also, will the anemones sting, sting the crab? <Nope, the crab's exoskeleton will protect it.> Any help will be appreciated. Thank You <Welcome, hope this helps. Mike G> 

Live Rock Hitchhiker crab 10/3/05 Hello!  I've been reading and enjoying WWM for a long time. After years of keeping various species of Loaches I've finally add a 30g saltwater set-up to my collection of tanks. It is a fish only w/live rock set-up and is fully cycled. It start off slowly, I added trio of one inch long, tank bred Ocellaris Clownfish, 5 Blue-legged Hermit Crabs, 5 Turbo Snails, 3 Bumblebee snails, 2 Peppermint shrimp and 2 Skunk Cleaner shrimp. On the first night the fish were in the tank one of the Clownfish disappeared without a trace. Not even a piece of a corpse was left. I thought perhaps the other 2 Clowns might have killed the third, but then I spotted this crab lurking in my live rock and I began to wonder if he might be the killer. He's a mottled greenish-brown color, about the size of a dime and never seems to venture out of the rocks. Any idea what he is and if he may have killed the Clown? Thanks in advance for your help and for such a cool Web site!  Robin <Crabs are hard to ID, but they are almost universally untrustworthy.  The crab may not have killed your clown, but between it and the bumblebee snails, they could have made quick work of the carcass.  I would suggest trapping it.  This is usually easily accomplished by placing an upright baited glass in the tank with the edge of the glass against the live rock.  The crab will fall into the glass seeking the bait, but will not be able to climb the smooth walls to escape.  Best Regards.  AdamC.>

Xenia Crab  9/8/05 Hi, First of all thanks for all the help I have gained from your fantastic site. I have read so much here that I had to get new glasses. (Haha)  <Glad to hear you have benefited and hope you are kidding about the glasses!> My question is have you ever seen a crab that lives in Xenia? I have had this Xenia for about a month. I put it in my display tank about a week ago and noticed a crab living among the polyps. He blends in very well and is hard to see. It does not seem to eat or pick at the Xenia. The polyps pulse all around it as if it is not there. Is it ok to leave it in there or should i remove it? Any info would be appreciated. I have attached a picture. Thank You <Congrats on finding such a neat critter!  I have seen these before in my own tanks and found it to be harmless, although I would keep an eye on it.  Best Regards.  AdamC.>

Problematic Hitchhiker - 08/21/05 Hello Wet Web Crew! >>Hi Tina!>> I attained a fair amount of live rock from a girl who works at a LFS who told me she needed to downsize her tank due to little time. <<ok>> I happily accepted her offer for half-price live rock that has been in her tank for a few years and has some decent algae growth on it.  When putting it into the tank, I found that the live rock wasn't all I was getting.  Nestled deep inside one of the rocks was a crab peering back at me. <<uh oh>> I immediately called the girl and asked about this guest in my rocks.  She told me she had emerald crabs in her tank, so it was possible that an emerald scooted in there while she was loading it into a bucket for me. <<Yes...possible.>> I quickly looked up emeralds online and found the pictures looked nothing like him. <<Ah, research...excellent!>> He is about the size of a half dollar, tan in color with red striping.  Not a thing like the green critters shown! <<No...and likely a menace rather than not.>> I called her back and said "are you SURE that he isn't something else?"  She told me that she got the rock directly from the reef, so it is possible that something hitchhiked in on it that she was not aware of. <<Mmm...obviously something "did"...>> Here is the problem...I'm setting this tank up for seahorses, and an aggressive crab species would not mix, as you know!  If he were an emerald, which I don't think he is, that might be alright but I cannot risk a mystery crab injuring, maiming or killing my future horses! <<Even an Emerald Crab would be dangerous, and I would definitely not leave this critter in a tank with seahorses.>> Any ideas how to get the little bugger out?  I've heard soaking in freshwater will make him vacate.  Is that safe for the live rock? <<no>> for him? <<probably not>> Any suggestions for me?  All advice is very appreciated. <<Couple ideas... Remove the rock harboring the crab to a bucket with some tank water...drop in a piece of table shrimp as far from the rock as possible...cover the bucket to block light...if all goes well, the crab will leave the rock for the shrimp so that when you come back (walk softly to avoid vibration) in about 15 minutes, you can quickly uncover the bucket and snatch the rock out before the crab can retreat back to its hole.  Another option is to sink a glass container in the substrate of the tank containing the rock and bait with shrimp.  Usually...once the crab enters the container for the shrimp, it will have enough difficulty scaling the smooth sides of the glass as to give you enough time to capture.  If both these fail, your only option may be to permanently remove the rock (with crab) from the system.>> Thank you very much for your time (on behalf of me and everyone who picks your brain without saying thanks!) <<So...that's what that tickling sensation is...>> Tina
<<Regards, EricR>> 

Death of Blenny: Whodunit? Around Christmas my eyelash blenny disappeared without a trace. <Oooh, sort of sounds like the beginning of "A Christmas Carol"> Attached is a photo of one of the prime suspects, a hitchhiker from Fiji. This looks to be exactly the same species presented at the bottom of your page http://www.wetwebmedia.com/swcrabidfaq2.htm, though no positive ID is given. His carapace is only around 1", total diameter 2 to 2 1/2". Claws are of moderate to large relative size. This fella is very strong and it took me a week to get him out of his little lair. <I see> The other main suspect is a Mithrax crab (maybe 1.5" carapace), but the blenny happened to be sleeping in the same rock as the hairy yellow crab (just around the corner), and that crab had been getting more bold in recent weeks. Plus, just look at his face! <Threatening!> (Note: I also periodically lose a snail here and there along the way, although as always those could be hermit-related.) <Yeah...> Any id on the crab species is much appreciated. <Don't know> Also: what do folks do with their unwanted hitchhikers? I can post to local bulletin boards, but no guarantees there. My LFS doesn't want it. I don't particularly want to euthanize it...though if it comes to that, can someone suggest a humane approach? Smash it with a hammer? (R.I.P. Blenny) Regards, John Berliner <Some are relegated to sumps, others kept in perforated "jails" in tanks... others taken to fish club meetings for others with more suitable environments... to stores. Bob Fenner>

Become a Sponsor Features:
Daily FAQs FW Daily FAQs SW Pix of the Day FW Pix of the Day New On WWM
Helpful Links Hobbyist Forum Calendars Admin Index Cover Images
Featured Sponsors: