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FAQs about Marine Crab Compatibility, Removal Strategies... 3

Related Articles: Crabs, Hermit Crabs,

Related FAQs: Marine Crab Compatibility 1, Marine Crab Compatibility 2, Marine Crabs 1, Marine Crabs 2, Marine Crabs 3, Marine Crabs 4, Marine Crab Identification, Crab Behavior, Marine Crab Selection, Marine Crab Systems, Marine Crab Feeding, Marine Crab Reproduction, Marine Crab Disease, Micro-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,

Shrimp and crab compatibility     5/29/17
Hey guys!
I have a 45 gallon mixed (lps/softies) with about 45 pounds of rock. It currently houses various snails, hermits, a fire shrimp (Lysmata debelius), a blue porcelain crab (Petrolisthes spp) and several fish. Three of those fish are potential "shrimpivores and crabivores"...a redlined wrasse, a carpenters fairy wrasse, and an orchid Dottyback. Is there an appropriate species of shrimp that you would chance adding to the tank, and would it be appropriate to add an emerald crab or two?
<Mmm; well; given plenty of hidey holes (for molting, soft-bodied periods); most any of the larger shrimps would/could go here. I'd have you read here:
scroll down to the "Shrimp" tray; read at the family level. I'd avoid Stenopids and am not a fan of Mithraculus... as you'll see by reading re them on this same page>
Thanks so much for always being there!
<Welcome. Bob Fenner>

Possible Xanthid Crab?     5/22/16
Good evening Bob and Company!
<Hey Suse!>
Thank you so much for your fabulous website; you are an amazing resource.
<Glad to share>
I keep a 60 gallon seahorse and soft coral reef (primarily sun corals and assorted sea fans) and always acquire all of my livestock (aside from the seahorses, which come directly from the breeder) from a single local shop that I trust.
Tonight I brought home a piece of live rock with mixed colonies of clove and daisy polyps (it’s lovely) - but about an hour after introducing it to the tank, I noticed it “breathing” - which, of course, neither of these species do. A brief investigation with a flashlight and a pair of long tweezers revealed this little guy hiding beneath the polyps. (Photos attached.)
<I see this Decapod>
His legs are much hairier than they appear in the photos - like the legs of a Mithrax crab (but his pincers are clearly wrong for Mithrax).
I pulled the rock from the tank at once, nudged the crab into a bowl, and shot these photos. After spending about an hour on your site, I suspect he’s a Xanthid - and that it’s a good thing I removed him before he could cause any havoc. Can you confirm his species, or at least let me know if I should keep him away from the seahorse reef?
<It is a member of this family; and I would keep it out of your seahorse system>
(My husband thinks he’s cute, but I don’t think my softies and seahorses will appreciate this particular variety of cuteness.)
<Mmm; if you have a live sump; I might place this crab there; where it can do no harm>
Thank you for all you do!
<Certainly welcome. Thank you for sharing. Bob Fenner>

Duncan coral flash damage... flesh? Decapods         5/1/16
Hi first I would like to say thank you for the great information that you provide, I am new to saltwater and all that goes with it and I get a wealth of information from you.
<Thanks from the crew.>
I have two emerald crabs that are feasting on my corals I have tried feeding them more so they will not munch on the coral but their appetites seem endless so with that said I have caught them and they are jailed in my tank until my LFS opens today in which they will be returned and hopefully sold to someone that can appreciate them for what they are.
<Crabs in general are opportunistic little beasts who will go for almost anything they can (shred) and fit into their mouths. That said they are fascinating in their own right and worthwhile. Just be sure you know what you are getting into, but certain kinds have particular uses as anti-algae weapons vs. "bubble" algae and so on, as you will no doubt have read on WWM. Generally untrustworthy however.)
The emeralds have eaten a good bit of flesh off the base of my Duncan coral, will the flesh grow back?
<A healthy colony should have little trouble recovering from non-catastrophic damage. They are surprisingly resilient although there are no guarantees. I wouldn't lose sleep.>
should I dip it in coral RX or Iodine mix to prevent infection or should I just leave it alone and see what happens. Thank you again for the great service that you provide.
<I'd watch it, leave it alone, and see how it progresses before moving onto disruptive treatments. If it seems to be going downhill (melting, discoloration) then the dip might be worth looking into. A "wait and see" approach would be my approach...should recover fine, just monitor it, keep things clean in the system, keep it fed. Some target-fed meaty foods will be appreciated. -Earl>

Is this crab ok for reef tank        1/24/16
I'm just new to the hobby, I live in Scotland, I have just set up my tank about 2 months only have
Clean up crew of snails and hermits and a few soft corals , this guy obviously hitch hiked on my live rock, he doesn't move all day and only when it's pitch black .
<Ah yes; looks to be a Xanthid (member of that family of crabs); not "very" safe... I personally would remove, or at least isolate (in a sump; an enclosed area...) away from your corals, fishes. May sample in time.
Bob Fenner>

Live rock and dreaded hitchhiker crabs; comp./control      4/29/13
Hi folks!!!!! Loving all the forums, and your help and suggestions for my specific questions have been invaluable!
But, here goes: 29 BioCube, parameters good, 20 pounds of live rock.
Livestock is: two Percularis clowns, one Banggai Cardinal, and a Fireshrimp.
Unfortunately though the live rock came with its fair share of hitchhikers.
We thought we had gotten all crabs out, but to my horror found two more today. We pulled the chunk out, and attempted to do away with the intruders. Traps never worked,
<Try other traps, baits>
  and we always had to resort to poking them with a coat hanger.
Well, this time we had to take drastic measures and freshwater dip the chunk of rock. And instead of two crabs, we came away with six!!!!!! The rock was only in the water for about 30 seconds. And we took saltwater from our tank and let it soak afterward. We did away with the saltwater it soaked in once we were finished and had cleaned our tank up a bit.
Now comes the part where you folks chastise me and tell me how many things I did wrong!!! Everyone in the tank seems fine, still doing their fishy/shrimpy thing. Should I expect something bad to happen in the next few hours?!! Help!!!!!
<You're doing fine. Not to worry. Bob Fenner>

Crab ID please; comp. f'       4/23/13
I think I have the same crab as a previous request for ID who sent a photo.
Here is a copy of the request.
Reef Aquarium Hitchhiker Crab ID Needed? 9/26/08
Hello, I wondered if you could identify this crab?
Thank you in advance~
<Mmm, I can't seem to find in my ref.s... Can you wait a till 10/6 or so?
Will ask LynnZ to look at. BobF>
I hope it is ok to do this.
<<Ah yes; referring to others work (in this case a photo) is fine>>
 The crab came with a new piece of live rock and stays in a crevice usually only waving a claw out to pick things of the rock. I have, however seen it just out a couple of times but only for a matter of seconds and no time to take a photo. It is very similar to the picture above. It has faintly striped legs like a Pom Pom, a dark oval carapace which is about 10 mm across and has markedly unequal claw size which are quite long for the size of the crab. It has a delicate claw with a thin arm and a much more heavily built one, again, very similar to above. I would be glad to know if I can leave it in my small 30 L Nano tank as it will be very difficult to catch.
<<I would likely leave it there for now... All decapods/true crabs are opportunistic, will try to eat other animals; but this one is small, may stay small, not pose a problem. If trouble, it can be baited/removed later>>
Nevertheless, I do not want it to damage my barnacle blenny (he's quite tough) or my blue stripe pipe fish who keeps sticking his head in its lair.
Any advice would be greatly appreciated.
<<You have it. T'were it me/mine, I'd hold off on removal at least for now.
Bob Fenner>>
Re: Crab ID please, another lifted pic      4/26/13

Hi Bob Fenner,
Thanks for your reply and I will follow your advice. I think I have tracked it down as Tanaocheles bidentata on an obscure online classification book which happened to include a photo
<I see this>
This is identical as far as I can see but info for it, on the net, is very scarce with nothing more than its taxonomy classification. I was hoping to find out something about its habits and its likely fully grown size. If you have any info on this crab I would be interested to hear. Thanks again for your help and great website.
<I do not; but thank you. BobF>

Malevolent Crab? 4/2/13
Dear crew
<Hello, Lynn here today.>
I have a few of these crabs in my reef tank and don’t know if they are the kind I should have in there or not. 
<The short answer is no, since, at least the one photographed, is a “true” crab (brachyuran: two claws + 4 pairs of walking legs) as opposed to a porcelain/”false” crab (anomuran, family Porcellanidae:  2 claws + 3 pairs of walking legs).  Brachyurans can have leanings towards various foods but they’re opportunistic omnivores that will eat just about anything when hungry and/or given half a chance. 
The longer answer involves examining the claws in order to get a better idea of a crab’s main diet.  Judging from what I see in the photo, your crab most likely has spoon/spatulate-shaped claw tips.  It’s believed that these are useful for scraping algae, etc., off hard surfaces, grasping filamentous algae, and/or scooping up soft materials (e.g. detritus and/or coral mucus).  It would be nice if these claw tips were indicative of a single family or genus, but they are found in many.  These crabs tend to be a bit better risk in reef tanks than say, a large, heavy-clawed Xanthid, or a more slender, sharp-clawed portunid (swimming crab), but by no means does this make them “safe”.  They're still opportunistic omnivores that may be fairly well-behaved when small and well fed, but can be a problem later on as their bodies and appetites grow, and competition for food increases.>
I did not purchase them.  I guess they would be around 6 years old. 
<I can’t tell how large the one is in the photo, but even if the crabs you have are a smaller species, they are still capable of damaging livestock.>
They only come out at night.  I've lost a few small fish and can't seem to keep any shrimp around.  I figured maybe these crabs are the reason why. 
<That could be part of it, especially if the crabs are able to grab a shrimp when it's vulnerable during a molt.>
Any thoughts?
<Yes, if possible, I would trap/capture the crabs and find them a new home in a sump or elsewhere. Please see WWM regarding crab removal (3 pages, starting here: http://www.wetwebmedia.com/swcrabcomp.htm >  
Thank You
<You’re most welcome.>
L. Splitter
<Take care, Lynn Z>

Re: Malevolent Crab? 4/4/13
Thanks Lynn.
<You’re very welcome.>
The crab, with its arms extended is about a 5 inch span.  The head is about 1.5 inches across.
<Whoa, yep, I’d be finding those crabs a new home!  Take care, Lynn Z>

Desperately seeking crab removal advice     8/9/12
Hello Crew,
I am starting up a new tank.  I have my live rock (Fiji rocks) curing at the moment.  In fact, it has been more than 4 weeks curing.  I was about to place the rocks in my display tank.  I picked up one piece, to my surprise, 2 or 3 little crabs went scurrying into the rock crevices. These are small little crabs, about half the size of a penny (or smaller). From reading your Crab FAQ sections, I know crabs are bad news for a reef tank or most tanks for that matter.  I want to remove them.  What removal method would you advise?
<... trapping... As posted on WWM>
  I was thinking a freshwater dip for the live rocks.  But this would mean I have to re-cure the live rocks.  Very much appreciate your advice.  Also, thank you for the wonderful service through out the years.
Warmest Regards,
<And you, Bob Fenner>

coral guard crab    4/15/12
Dear Wet Web Crew,
<Hi Wendy, Jordan here>
I’ve purchased a 3” Stylophora and have just found that it contains a commensal crab.
<Nice freebie.>
From the size and shape of it I believe it to be Trapezia.  The coral and crab are currently in quarantine, but will go to my 180 gal reef tank afterward.  I would like to know if you would consider the crab a hazard to any other corals (or fish), and your opinion on whether the small colony of Stylophora would do better with or without it?
<I would leave the crab in the coral. The Stylophora is large enough to withstand any damage the crab may inflict. Smaller SPS should be safe as the crab is going to find the larger colonies. It will threaten fish which venture to close to its home but it's too small to do any real damage.>
I have read that these crabs eat coral mucus as well as coral flesh and that this may be detrimental for a small colony, but also helpful for growth, and that they may migrate to another coral at night, but only reside in Pocillopora or Acropora (but am wondering if they really may go into other corals as well such as a Tubastrea?
<They will stick to SPS.>
 I have a very nice Tubastrea which I would not want the crab to damage.
<Tubastrea would likely eat the crab if it tried.>
My reef tank also contains another 3” Stylophora, a couple of 8 inch Staghorns, a few Birdsnests, plus other assorted LPS and Mushrooms,  and an assortment of fish (Argi, Tangs, Anthias, Fairy Wrasses, Gobies, Chromis, Clownfish) . 
Thank you for your advice,
<Quite welcome>
Trapezia crab id    4/15/12

Dear Crew,
Attached is a picture of my hitchhiker guard crab which I wrote of earlier.
 Could you comment on whether this crab appears to you to be a Trapezia, or other ?
< I suspect it is Trapezia digitalis but it is difficult to say for certain based on the picture. It is either a Trapezia sp. or Tetralia sp. The two can be easily differentiated by there claws. Trapezia sp will have claws equal in size; Tetralia sp will have one claw larger than the other. Tetralia sp are also smaller and will only host Acropora, Trapezia sp are not as picky as to which stony coral they call home. Nice hitch-hiker regardless of genus>
<Quite welcome>

Montipora Eating Crab 1/23/12
Dear Crew,
I hope that you are doing well!
<And you>
I just wanted to request a quick ID today if at all possible. One of my Montipora digitatas was bleaching a bit at the tips and today, I found this little guy attached! So sorry, about the picture quality but these were the best shots out of about 25. It's definitely a crab, brownish/red in color, hairy arms as well as barely visible pinchers (sorry, no microscope). This is the only one that I've witnessed so far and it seemed to arrive when the Montipora was added to the tank. I'm almost certain that it was a hitchhiker. It was accidentally killed upon extraction from the coral.
Should I be on the lookout for more? My hunch is that it is a loner.
Lastly, in your opinion, should I break off the dead section of coral, or just leave as is?
<Well, hard to say, make that determine, if this little Decapod is much of a real or potential risk to your Montipora... the group is generally omnivorous... but there are many crabs (e.g. Trapeziids) that are found in close association w/ Scleractinians, Alcyonaceans, Pennatulaceans... and more Cnidaria, that are more commensal than not. Some known to keep off other predators, improve circulation...>
Thank you!!
<Up to you to remove or no of course. Bob Fenner>

Black Crab problem.. 11/21/11

I have a reef tank with several residents both large and small. One of them happens to be a fat little black crab that had been a hitch hiker on a large porous rock with several caves.
I think this crab is responsible for a few of my smaller bottom dwelling inhabitants. I've tried to lure it out with food, but the hermits are all over it.
Do you have any other suggestions other than taking this large rock out and disrupting the whole house?
<Mmm, yes. I'd bait/trap out all (and save the organisms not to be removed... in a floating colander perhaps), till you've caught this crab to remove. See here re: http://wetwebmedia.com/swcrabcompfaq3.htm
Bob Fenner>

Crab ID, removal 10/13/11
WWM Crew,
I finally evicted the crab that had been munching on my button polyps and macro algae. I believe it to be a gorilla crab,
<A Xanthid? Mmm, maybe... I don't see the usual distinctive dark tips on the principal claws>
but please let me know what you think. He is on his way to the LFS to see if they want him. I tried leaning a prescription pill bottle up against the LR with some mussel in the bottom, but the next morning, the mussel was always gone, with no crab in the trap. Not sure how he was pulling off the heist, but he seems to be a very smart little crab (outwitted me for almost a month). I finally pulled the rock out that I've seen him hiding in and poured RO water in the hole which got him moving,
then I used a toothpick to poke him out from the back side. It was a pain, but I got him out and got to re-arrange the rock-work in my tank. Since I had the rock-work taken apart, I also did a RO dip of all the other LR and evicted about 5 flatworms that had previously gone unnoticed. Win-win!
Thanks for your advice on the matter, you guys/gals rock!
<Mmm, read here: http://wetwebmedia.com/SWCrabIDF18.htm
and the other 17 Decapod ID files linked above. BobF>

Mystery Crab! How to Trap a Crab -- 7/20/10
Long time no talk!
<Hi Melissa, Lynn here today!>
That's a good thing!
I hope all of you are doing well.
<Yep, we're hanging in there, thanks.>
Short run down on my tank again since it has been a while. Some equipment has changed too. 125 gallon tank roughly 125 lbs live rock DSB, Remora Pro, Needle Wheel, (incidentally both of them combined with water changes finally nipped my red slime in the bud so just kept them running ;)
It helped that I stopped the kids from feeding too!)
<Kids do love to feed fish, but it can sure lead to problems!>
Inhabitants: lawnmower blenny, 4 blue green Chromis, ocellaris, yellow tang, six line wrasse, coral beauty, royal gramma, Blue hippo tang, Chocolate chip starfish (Chip) (he is getting huge and getting his own tank shortly!),
2 cleaner shrimp, 4 Mexican Turbos, roughly 20 Nassarius snails, 20 Trochus snails, 40 blue leg crabs. Herein lies the problem. I apparently have a crab!
<Uh-oh. The funny thing is that I was just thinking the other day that it had been awhile since we'd gotten a good crab query.>
A large crab. Almost as large as my palm.
<If the carapace is the size of your palm - yikes! If the whole thing, legs and all, is that size, that's not too bad but the crab will need to be trapped/removed.>
I did not purchase said crab and put him in there.
<He's probably been in there awhile.>
He looks to have hairy legs and two big claws. My best guess would be Mithrax or Emerald although it was not green it was definitely beige-ish.
It was very shy and skittish.
<Understandable. That's probably why he's gone undetected for so long. Chances are good that up until now, he's done most of his foraging at night.>
Grabbed an algae wafer right up and went to town. I had put one in for the blenny and he grabbed it instead.
<Yep, now that he's fairly sizeable, he'll require more food and become increasingly bold in his attempts to get it. An opportunistic, hungry crab is not a good thing around fishes or other desirable livestock.>
I will try to get a picture but I doubt I will have much luck with that.
<That's okay. Basically, a crab that large is better off in its own tank or with other 'tough guys' that won't end up as prey.>
I have a net buried in there now in hopes of catching it. Again, not likely.
<Crabs can indeed be a challenge to capture/trap. Choice one includes hoping the little fellow comes out of the rockwork far enough so you can net him. Unfortunately, they're wary and quick, so that rarely works. Choice two involves going Rambo on the guy and tearing the tank apart to get to him. That's never fun and should only be done as a last resort. What I recommend is choice three: baiting him. The advantage of this is two-fold. First of all, keeping the crab fed helps deter predation and allows you time to desensitize him to your presence, as well as that of a net or other trap/set-up. With a crab that size, you'll need a fairly large net, jar (like a clean, wide-mouth pickle or mayo jar), or even half of a plastic water bottle. Unfortunately, the above methods require your presence in order to complete the capture, but it's better than taking a tank apart! If you're going to use the net method, place it near an open area of sand (maybe near a corner to limit his escape routes) and lure him closer each day. Hopefully, he'll come to associate the net with being fed or at the very least, not see it as a threat. Once he's comfortable approaching the net, reach in, grab it, and get him. You've probably got one shot at this method before he gets wise to what's going on, so make it count. As for the jar/bottle method, there are two ways to go. For something like a heavy pickle jar, tip/wedge it against the rocks (where you think he hangs out) and bait him in there. Once inside, he won't be able to climb up the slick walls and will be trapped (unless he can reach the lip). You can probably leave this type of trap in there overnight, unattended. As for the plastic water bottle method, you can use either end of the container. Just make sure there's enough room for him to get in and not get out quickly. Using a hole punch, place two holes about an inch or so apart and about an inch or so away from the open/cut edge, and attach some fishing line (enough to extend out of the tank). Lay the container on an area of open sand and bait him closer over several days (however long it takes). Eventually, use something like a turkey baster to get the bait inside the container towards the back. Watch and wait for the crab to go in. All you have to do then is grab the fishing line and pull him up! If you use the top half of a water bottle, and remove the cap, it's easier to pull up since the water inside has a place to flow through. The small, open lid also gives you a handy place to aim some food to the back of the trap. I know all of this sounds like a time-consuming pain but it's worth it. It's either that or go Rambo on the guy!>
As for how it got there, I have not purchased anything for quite some time. The last thing was the Blue Tang and I certainly would have noticed a crab with it.
<No kidding, so would the Tang!>
And ironically even my rock was not "live" I bought the stuff dried in a box. My first piece of live rock was almost 4 years ago or whatever. I have done the rest on my own. I am thinking it came with the other crabs a few years ago and I did not notice it.
<Possibly so, or in with that rock from four years ago.>
The question is, Do I keep it or no?
<I definitely wouldn't keep it in the present tank.>
Can I put it in the other tank with Chip? He is a large starfish. He is easily 8 inches across now.
<Wow, that's a big one. I'd go ahead and put the crab in with the star, keep both well fed, and see how it goes. If you see any signs of predation, remove one or the other right away.>
I only have live rock in the tank currently, but feel comfortable enough with all of my equipment and knowledge to move on up to corals.
<Good for you for being patient and not jumping into corals right away!>
Anyway, the crab freaked me out. It is big and hairy. I thought it was an octopus at first glance.
<Hehehee! I had an epitoke (a Polychaete in a reproductive phase) scare at least ten years off my life a few years back so I know the feeling. I'm embarrassed to admit that I screamed like a little girl!>
I do not know how in the world I could have missed it.
<Again, he'd probably been hiding out in there for awhile, only coming out at night.>
There is so much rock work though it got away from me almost immediately.
<That's frustratingly typical.>
I am worried about my fishy friends. Your advice is much appreciated. Thanks again!
<You're very welcome and good luck!>
<Take care, Lynn Z>

Sally light foot, and Stenopid comp. 7/12/10
I'm back with more reef questions...
I have a 180 gallon tank (empty but with water/rock) and I was wondering if a mated pair of coral banded shrimp and 1 sally light foot crab would be okay together.
<If they don't get too hungry>
Except for a fair amount of snails
<They may eat these>
as the only other invertebrates, these guys would be pretty much the only inverts in the tank. Fish-wise, there would be a school of green Chromis', 1 Pseudochromis, a Sixline wrasse, a algae blenny and 3-4 PJ cardinals.
Would this overall combination work, again a 180 tank [6'x2'x2'], or should I expect WWIII between one or more things in the tank?
Thanks in advance,
<See WWM re crab and boxer shrimp compatibility. B>
Sally Light Foot/Sally Light Foot Compatibility/Crab Compatibility, James' go 7/12/10
<Hi Tristan>
I'm back with more reef questions...
I have a 180 gallon tank (empty but with water/rock) and I was wondering if a mated pair of Coral Banded Shrimp and 1 Sally Light Foot crab would be okay together.
<I would not chance. When large, they are capable of catching and eating shrimp and other invertebrates.>
Except for a fair amount of snails as the only other invertebrates, these guys would be pretty much the only inverts in the tank. Fish-wise, there would be a school of Green Chromis', 1 Pseudochromis, a Sixline Wrasse, a algae blenny and 3-4 PJ cardinals. Would this overall combination work, again a 180 tank [6'x2'x2'], or should I expect WWIII between one or more things in the tank?
<Looks like a peaceful clan. The Sailfin/Algae Blenny (Salarias fasciatus) does better in aged systems where some algae is present. If not, supplemental algae feedings will be required. May want to read here. http://www.wetwebmedia.com/algaeblensart.htm>
Thanks in advance,
<You're welcome. James (Salty Dog)>
Re Sally Lightfoot... now Mithraculus Compatibility/Crab Compatibility 7/12/10 - 7-14-10

Hmmm...(thinking about your reply)
Both you and Bob said that the two would not get along, I didn't expect that they would, I was just crossing my fingers and thought I should ask, hoping the tank may be big enough. Would a handful of Emerald Crabs be okay
with the Coral Banded Shrimp?
<Generally safe, but they are an opportunistic feeder, and if food is not available to them, they may turn to supplementing their diet with corals or invertebrates.>
Otherwise what non-hermit invert would work; helping to keep the bits of macroalgae growing in check? I'm a bit reluctant to put in a urchin because I don't want it to knock stuff over and I would like to keep as much of my
coralline algae as possible. I'm at a bit of a loss as to what could work.
<The Blue Tuxedo Urchin (Mespilia globulus> would be one, as they are much more forgiving in terms of rearranging your rockwork. You may want to read here and related links in the header for methods of controlling algae.
http://www.wetwebmedia.com/algaeconMar.htm. James (Salty Dog)>

Re: Monodactylids and Crustaceans, predators for the latter 5/24/10
Thank you for the reference to the website. It should help a great deal with species-specific information.
I was wondering what you meant by purposeful predator control. I take that to mean finding something that preys on crustaceans and using it to prevent the crabs from overrunning the tank. If so, do you have any suggestions as to organisms that love eating crab as much as Boston?
<Mmm, the groups that come to mind are Balistids, some larger Labrids, Stomatopods... You should be able to find input re these and other crabs principal predator groups in a library search, maybe even the Net. B>

Crabs, control 4/13/10
Hi Bob,
I've got a crab problem due to some aqua cultured rock, and I'm seeing why a lot of people like to use dry base rock.
I've instigated 2 major battles against Xanthid crabs since I started the tank, and I guess pulling the rock and flushing every hole with freshwater didn't get them all to run off. Now, about 2 months later, I'm catching as
many crabs per night as I was before I did the house cleaning where I caught about 65 crabs. I found that they were in the tank because they're bothering some of the corals (Pretty much everything that isn't a Goniastrea or
Acanthastrea; it appears that they're living inside the Astreas, but not hurting them too much, as they will still eat normally. Are gorilla crabs known to be commensal or symbiotic with corals?)
<Can be... but if too many, hungry, can be trouble>
I'm wondering if there are any shrimp, fish, or other additions to an aquarium that are heavily biased towards eating crabs, gorilla crabs in particular.
<Best to trap them out>
I know mantis shrimp would be an effective option for crustacean elimination, but I'm not sure if they would be a good fit, as there are young kids who may tap on the tank and "taunt" one to the point of breaking the glass,
an outcome I wouldn't be able to handle financially or emotionally after all the work that has gone into this tank. Are there any other, slightly less risky shrimp or other animals that would fit into a "crab control" role?
Andrew Angrist
<Trouble is, a predator may consume other livestock you'd like to keep as well... Please read here:
and the linked files in the series above.
Bob Fenner>

Crab ID 1/4/2010
Hello Crew.
I am in the process of trying to catch some of the crabs in my Red Sea reef tank. Most all need to go. I have already caught one shamefaced crab.
There is at least one more of these. I have attached a picture of one crab that may be ok to keep. I believe it to be a Black Mithrax. Note in the picture the round plates at the end of the pinchers. He feeds heavily on algae, but obviously will consume meat as a small piece of shrimp was used as the bait. Should he stay or go?
<Mmm, please see Lynn's input on our forum, here:
Also, many of the other crabs are very small and I have not had luck
catching them in the traps. Only the larger crabs get caught. Is this normal?
<Not atypical, no>
I am using a small canning jar tilted against the rock with a small piece of shrimp in the bottom. Is there a better trap for smaller crabs?
<Whatever works... the small, all-plastic rodent traps (or repackaged/labeled ones for aquarium use) from Home Depot, Lowe's et all... are my faves... have a dropping un-openable (by them) trap door... aka "Have-A-Heart" traps for terrestrial use>
Thanks again for all the great information. I am certain I would not be having the success I am having without this site.
Kind Regards,
Erik Hayes
<Welcome! Bob Fenner>

Coral Attack, Zoas vs. Decapods 9/16/09
Need more help.
<I know I do>
I have a 135 with 150lbs of live rock. Nice and purple. Nitrate is less than 10 and on its way down, as I just installed a RDSB. I found a single Zoanthid growing on the rock and figured it was a good time to put a few test corals in. I put in a small frag with about 10 Zoanthids. The Zoas were attached to the skeletal remains of something. It was not a rock. The first night one of the hitchhiker crabs apparently removed the coral from their attachment and took the structure away.
<Wow; strong crabs>
I found the Zoas on the bottom curled into a ball. I have replaced them in another location and they are slowly moving up the rock.
Is any of this normal? Will the Zoas recover?
<Mmm, hopefully. You might want to rig some sort of strong cover over them for now. Maybe a plastic "berry" container, inverted, tied down with all-plastic ties.>
I have seen 3 crabs. Based on their claw configurations, 2 need to go.
The last time I tried trapping, nothing happened. I assume crabs do not hunt during molting?
<For the most part this is so>
I found sheds during the time I tried the trap.
I really appreciate all the great information on the site and in the Bob's books. The entire family is having a great time learning and watching new things happen every day.
<Ahh, great! BobF>
Erik C. Hayes

Decorator Crab; Feeding And Compatibility 8/30/09
Okay, so my roomy and I recently set up a 25 gallon salt water aquarium consisting of crushed coral and about 8 lbs of live rock. We decided to throw in a Spider Decorator Crab to entertain us while we
wait for the tank to finish curing and ammonia levels to get as close as possible to zero :) (we made sure they were pretty darn close to nil before adding the crab).
Squeegee, as we named him, seems pretty content, scavenging the tank for whatever he can find on the live rock, not-to-mention the assortment of tropical flakes that we throw in on a day-to-day basis.
This leads me to my first question. Are the flakes enough for the crab to eat and if so how many should I be throwing in there? Also, would feeding the crab ghost shrimp be okay (if so how many a night)?
<Ghost shrimp are fine, maybe one every other day depending on the crab's size. Kind of pricey for crab food.>
And lastly, Is there a more ideal (and cheap?!) sustenance we could be feeding it?
<Flakes are fine and about as cheap as you can get. A few flakes per day should keep him happy. Crabs are opportunistic scavengers and will eat most anything they can find.>
Finally, as far as compatibility goes... the tank was originally intended for a Snowflake Eel (no fish) which we'll be getting as soon as the tank is ready. Do you think a young (6in) Snowflake would attack/devour Squeegee?
<A excellent chance for this to happen as crabs and shrimp are their main diet in nature. Do be aware that your tank will eventually be too small for keeping a Snowflake Moray in good health.>
Would there be any way that we can get them accustomed to each other with adequate feeding long enough so that they can coexist for some extended period of time?
<No. Do read here. http://www.wetwebmedia.com/snowflakemoray.htm>
Thank you!
<You're welcome. James (Salty Dog)>

Black Mithrax Crab HH, incomp. 8/7/09
Good morning crew,
<Hi Jessy here>
I have a few questions about a hitchhiker. I've actually been trying to catch it for a month or so, but I've never had any problems with it until now. I have identified it as a black Mithrax crab. it looks and feeds like
an emerald but black with very hairy legs. (That's kind of a "duh" statement isn't it?) I recently had a pistol shrimp and a black ray goby pair up and make a burrow underneath my live rock. I came home one day to
find the shrimp gone and his goby hiding. Later the goby abandoned the burrow and the black Mithrax emerged from their den. The next day the goby returned for a while, and that was the last I saw of him again. The Mithrax isn't bigger than the goby, but could he have eaten them both?? I would think the goby would have protected his buddy, but maybe I'm confused. If this crab did kill them both, how do I trap the SOB?
<Jake, unfortunately that is probably exactly what happened to your poor pair. Those little devils of a crab are bad. To trap them, I've heard many things. They are much like mantis shrimp...hard to catch. I've heard of everything from a small glass jar being buried neck up in the sand for the crab to crawl into with food as bait, but not be able to get back out of.
I've heard of outright spearing the little buggers, but that seems a bit extreme and skilled. The last way I can suggest is figuring out what rock the little guy stays in and removing that rock from the reef to be flushed
out in fresh water or prodded until you can better see the culprit. Either way, it is not going to be an easy process. I wish you luck!>
Jake Maenius
<Regards, Jessy>

Zoanthids Disappearing, Hitchhiking Crabs -- 7/18/09
<Hello Jared, Lynn here this afternoon.>
I have been loosing the expensive Zoas fairly fast each night.
<Yikes! Have you looked for the usual suspects? Please see the following links for more information/photos: http://www.zoaid.com/gallery2/main.php?g2_itemId=384
http://www.wetwebmedia.com/zoanthidcompfaqs.htm >
The ugly cheap ones are doing great just like kudzu (of course).
<Murphy's law strikes again.>
I have lost a quite a few whole colonies of tubs blues, gorilla nipples, fire and ice, black cherry and so on. In all about $300 of Zoas!!!!
I pulled out my trusty red lens light 3 nights in a row and found this guy in a hole near the Zoas. Now I do not know if he is the culprit, as he does not have the really fuzzy bear legs or sharp claws on the ends (they are flat and look just like a emerald crab)....so a rogue algae eater gone to the dark side maybe????
<I don't think the crab was actually eating the Zoanthids, but it's possible that his presence was acting as an irritant. In which case, you'd have noticed the polyps remaining closed for extended periods of time (not disappearing overnight). I guess it's always possible that, for whatever reason, the crab was pulling the polyps off the rock. I just don't know. What you describe sounds more like deliberate predation. I'd look for Nudibranchs, Heliacus/sundial snails, and others listed at the above link. One other thing to do though is check the remaining Zoanthids for any sign of small light/whitish spots. If so, it could be what some hobbyists call Zoanthid pox. Please see this link for a photo example: http://www.zoaid.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=3573
For treatment, see first FAQ, titled 'Zoa Pox Treatment -- 05/09/09' at this link: http://www.wetwebmedia.com/furancpdfaqs.htm
More info here regarding diagnosis/treatment: http://www.wetwebmedia.com/zoanthidhlthfaqs.htm >
Plus he lost a leg battling me.
I accidentally skewered it with a bamboo skewer and was able to force him out of the hole that way. I have him in my fuge with easy access to remove him, but I have found 2 more EXACTLY like him in another piece of base rock. And of course they are either too far in or they scurry away before I can get them.
<No kidding. They know they can't win a battle against the skewer-man!>
Zero damage as of yet from them, but I am still trying to get them.
<I would do the same.>
He looks very similar to the header pic and last pic on: http://www.wetwebmedia.com/Arthropoda/CrustaceanPIX/SWCrabs/Crab%20IDs/swcrabid12.htm
<Gotcha. Although those claw tips look fairly blunt, they don't appear fully spatulate like those of emerald/Mithraculus crabs. Also, the presence of hefty molar-like ('molariform') structures on the inside edges indicate that the claws are less adapted for eating algae and more adapted for crushing -- usually mollusks. Crabs on the whole are omnivorous creatures. They're usually okay in reef tanks when small, but can be a problem as they grow larger.>
What do you guys think????-- Trigger/octopus food or not?
<Well, the trigger and octopus would definitely love it, but I'm a softie; I'd spare their lives and find them a new home in the sump or elsewhere.>
<Take care, LynnZ>

Crab stow away and dead shrimp/snails 5/1/09
We are new to your site and hope that you can help us. We have a 30 gallon marine tank and just discovered that we had a stow away crab. We assume it was in the live rock. We found two claws and a top shell that was about 1" and 1 1/2" across which was white with brown spots. The crab type really doesn't matter as we have lost 2 peppermint shrimp, 1 fire shrimp, and about 20 snails in the past month, so we hope to get it out of the tank.
The thing is, my husband moved our fish to a quarantine tank (hopefully to save them from becoming dinner, and he removed all of the sand as well to a couple bowls trying to shift to find the crab. He didn't find a crab but he did find 3-4 solid white mucus chunks with a few black lines in it. The chunks were about 1/2" each. Could this possibly be the remains of the crab if he squished it?
<Possibly, but he is probably hiding>
Last night we saw the first claw so we think it must have just lost it's shell. We want to know if we have accidentally taken care of the crab (by squishing him) or if he is most likely hiding in the rock. Needless to say we don't want to keep feeding him our daughters fish for dinner.
<A trap might be your best bet. Commercially available traps are normally pricey, but you can actually make one yourself by burying a glass jar in your sand bed and baiting it. The best time to do this is likely at night, the crab should go for the food and then have difficulty climbing out of the smooth jar.>
<I suggest reading here
Tami & Mark
<Your Welcome
Josh Solomon>

Decorator crabs. Comp. 04/03/09
Hi, i have 2 decorator crabs in one 30 gallon tank, they were fine when i brought them home a few weeks ago and were small. Once they got a little bit bigger it seems they try to eat everything.
<What they do>
I have never dealt with this type of decorator. It's the sponge decorator variety of crab.
<There's more than one species...>
Should i get rid of both or just one?
<... what do you want to have else-wise?>
I planned on getting a different species that i have had experience with but not this one. I was given these two when i ordered a different type of decorator.
<Mmm, I'd likely trade both in... you will have "issues" with one, two... in any case. Bob Fenner>

Need to rid my reef tank of an Emerald Crab! A Suggestion 3/23/09
<Hi there James, Mich with you.>
Great site by the way.
<Glad you like it!>
I made a terrible mistake and put two emerald crabs in my reef tank. Why a LFS would sell these things is beyond me
<They have their uses I suppose. But I personally am not a fan.>
but I was dumb enough to buy two, not one! I have found out the hard way that these crabs only eat coralline algae off of live rock, or better yet, coral polyps, and this is also based on other reefer's experiences with these crabs on other blogs. I tried your raw fish in a jar trap and the male went for it after a few hours and I got him out (yea).
The female crab will not go for anything even if its a few inches away and stinks really bad!
<Heehee! Perhaps the females of the species are smarter than the males?>
Is there any other way to get this miserable creature out of my tank if raw meat doesn't work?
<Well I don have a suggestion but I'm not sure you'll like it.>
I think I would rather pour bleach in my tank
and deal with that than watch this thing eat every polyp off my corals, oh yea, and my coralline.
<Well here's my trick. It sounds like you know where she lives. You need to remove that rock. Take that rock and put it in a long under-the-bed type plastic storage container filled about a quarter of the way with water. Elevate one side of the container and put the rock in the area that is the deepest. Then gradually over the course of say 2 hours or so move that rock higher up the incline so the rock is in ever more shallow water.
Make sure you put some PVC or some small rubble in the deep end of the water so the crab has some place to hide. But the crab in my experience will want to stay in the water and you will likely find her hiding in the safety of the hiding places of the deep end. I know you are probably not very fond of her right now. But please, this animal is doing what she has evolved to do, have mercy on her, care for her responsibly, move her to your sump, return her to your LFS or find someone who can provide her the care she needs.>
My tank is a RedSea Max 250 (65 gallons). Thanks for all your great support.
<I hope this helps!>

Good crab or bad crab?? 01/22/09 Hello Crew, I have several. Purchased from a fellow hobbyist as reef safe. He said that they are emerald crabs, but they are more Tan with dark green pigment than all dark green. <One of the troubles with common names... there are several species of Mithrax crabs that sometimes get lumped under the common name "emerald crabs." The green ones are the Mithrax sculptus. But there are other species which look a lot like M. sculptus, but that are more red or brown (some are even black).> I have had them for a few months with no damage, but I realize that I am not sure what they are, <Possibly M. forceps... but it's very hard to make much out in the photo.> which is a bit unnerving. (Yes, I should have been more considerate before adding them)/ The claws are light. If they are in fact bad, what is the best way to remove/catch them. <No crab is 100% reef safe. But the Mithrax crabs tend to behave themselves more than most when they're well-fed. They are good scavengers and algae pickers. I wouldn't remove them unless they start to become a problem (i.e. just keep an eye on them).> P.S. Pic is in the worst corner of the tank. Ignore the Kenya tree and Aiptasia please. Thanks very much, Mitch <De nada, Sara M.>

SW Crab Question, incomp. -- 01/13/09 Evening crew, from snow buried Chicago! <<Greetings Heather'¦ From a somewhat more pleasant South Carolina>> A few weeks ago while gazing at my tank, I discovered a new (well, not quite new, but now large enough to be noticed) inhabitant, a crab. <<Mmm'¦>> From the searching I've done with Google on WWM, the closest comparison I could find was the Banded Clinging Crab, Mithrax cinctimanus, but that is a rough comparison. <<Okay>> My crab is now about the size of a dollar coin, roughly an inch wide body. It is a dark brown/black base with orange markings or "patches". My tank is a 55 gallon with live rock, a Royal Gramma, two Ocellaris Clowns, two Skunk Cleaners, and five Peppermint Shrimp. The Peppermints have only been in the tank for two weeks. I did a head count last night (somewhat difficult to do with 60lbs of live rock...) and all are still present. I was wondering if I should be concerned about my newly discovered crab harming any of my other inhabitants, mainly the shrimp? <<Very possibly, yes 'and the fish too. Even if this is a species of supposedly 'reef safe' Mithrax crab, large specimens are known to pose a hazard re. If this is not a Mithrax species, the concern/hazard is likely even greater as this crab continues to grow>> If it does pose a threat, how is best to remove him? <<This can prove difficult'¦ A trap of some kind'¦ Perhaps a small jar baited with a piece of meat of marine origin placed in the sand or among the rock. Do also peruse WWM re 'crustacean removal' for other's thoughts/ideas>> It seems to us that he has grown since discovering him, so my hopes of him not getting any bigger are gone. <<Indeed>> Thanks much for everything you guys do! Mr. Fenner's book is one of my most read! -Heather <<Happy to share, Heather. Good luck with trapping that crab. EricR>>

Crab eating open brain?? 01/04/09 Hi there! <Hi> I have been spending a lot of time on your site and it has helped me tons! I have also listened to Bob (just bought your conscientious book) Blue zoo Radio which I listen to and love! I have a question I needed to write in for... I have a 29g mini- reef, running now for 3mos. Ph 8.2, 78 degrees. N , No2, and No3 all 0. Ca 380, KH 8. I am running a Current Satellite 30" 60w SunPaq dual daylight, dual actinic, w/moon for lighting. I am also using a hob filter using foam, and carbon, an AquaC remora skimmer, both hung on the back of tank, and 2 powerheads placed in the top front corners of the tank pointed to the opposite lower back corners of the tank. My tankmates are: 1 turbo, 1 Trochus, 1 emerald crab, 1 peppermint shrimp, 1 blue knuckle hermit, and around 8 mini hermits. I have a few small Seastars that hitchhiked into my tank as well. I acquired 2 colonies of Zoanthids, a sponge, some tube (feather dusters?) worms, and some mushrooms on my live rock. The corals I purchased, were acquired from the same LFS; Euphyllia Frogspawn, Dendrophyllia (my favorite) , Caulastrea Candycane, Xenia, Nephthea, Diaseris, and a Trachyphyllia g. (pink and green). All seem to be doing great, (with the exception of my Trach, which brings me to write to you) expanding fully and eating. <This is a lot of different types of corals for such a small tank. I would expect some chemical warfare problems... if not now, then in the near future.> My question is about my open brain. He's been in my tank about 5 weeks . I originally had him up on a rock, just an inch above the sand, but my pesky blue knuckle hermit kept mowing him over into the sand, along with everyone else! I have since used Aquastik to glue all my corals to the live rock, and put my brain onto the sand as I've read is better on your site. <Ah, good.> He seemed to settle in, expanding during the day, after having what seemed to be a tough few days. He did still eat a small mash of raw shrimp 3 days ago. I tried to feed him yesterday, and a puff of brown 'smoke' came out of one of his mouths. Good/bad?? <It is likely expelling waste (maybe even expelling Zooxanthellae-- judging from how it looks a little pale, this could be "bad").> Tonight, after my actinic lights shut off, I found my Blue knuckle hermit on the edge of my open brain. The hermit looked like it was shoving his legs and claws into the edge where the pink outside, meets the green inner side (where the brains mouths are) kneading it like a cat. I tried to move it away from my brain , but it grabbed hold, and wouldn't let go. I tried luring it off my brain with a piece of krill, but it was more interested in pawing at my brain for a bit longer until the brain was totally drawn into its skeleton. It finally lost interest and moved on . Was my Hermit eating my Open Brain coral?? <This is a bad sign. Hermits are mostly opportunistic eaters. It was likely either trying to steal food from the coral, or picking at weak tissue.> Is my Trach dying? Should I remove my Hermit? <Possibly, unfortunately-- but the good news is that it's far from dead just yet. Yes, I would remove the hermit and target feed the coral.> 2 last questions; What other corals do you think would be a compatible next purchase to go with the corals I already have? I would love to buy 3 or 4 fish. Any suggestions?? <IMO, you have too many different types of corals already. As for fish... keep them small and few, gobies, Chromis, maybe Perculas... please read, research thoroughly before purchasing.> I have attached a picture of my Trach that I took just yesterday, and a pic of where things are set up in my tank. Thanks for taking the time to answer my questions!! <Good luck>
Sara M.>

Hitchhiker Crab and Dwarf Morays, comp.s 12/02/08 Hello, <Hi Paul.> I recently ordered two Gymnothorax melatremus (Golden Dwarf Moray) and plan on putting at least one of them in an established 58 US gallon reef aquarium. Would it be advisable to put both eels in the same aquarium as they are not actually a mated pair? <Preferable, sometimes found as pairs in nature. Your two may become a pair and should only be separated if they start to fight severely, which is less probable even if they have the same gender.> If not I can place them in separate tanks easily. <I'd leave this option if fights should start. In this case one will more easily be caught with net.> My second question concerns a Xanthid crab that I recently found in the 58 gallon reef. More specifically, I found a molted carapace approximately one inch across along with claws and other bits of old crab exoskeleton. Will this crab pose a danger to the eel(s) if I put them in the tank before I can capture the crab? <If the eels are at least 6" they should rather be a danger to the crab. If they are significantly smaller I'd catch the crab with a crab trap just for peace of mind.> I already believe he has killed fish in the tank as a pair of Banggai cardinals went completely missing several months ago. I did read somewhere that golden dwarf morays would eat invertebrates, but would one be able to take down a crab of this size? <Depends on their size, physical condition, crabs are their favourite food. Healthy specimens of 6" should be safe, only dead/dying small eels (this reclusive and expensive species is sometimes caught with poison) may become crab food. I've seen relatively small morays tearing off pinchers of crabs they could not eat as a whole. They are able to tie a knot into their body and pull their head and the prey item through the knot.> In any case the morays will go into a quarantine tank, at least until I hear back from you. <Okay.> Many thanks, Paul.
<Welcome. Marco.>

An answer, rather than a question! Crab eating SPS 09/18/2008 <<Good day, Bob, Andrew today>> I see a lot of posts asking about crabs. Here area couple of very good pictures of one that I guarantee is an SPS-eater. <<Heeeee...i would certainly agree>> The coral he lived on was getting 'tracks' all over it of nipped out polyps, etc. After he was removed, the coral completely recovered. Feel free to use the pictures as you like. [IMG]http://i226.photobucket.com/albums/dd7/Coralmaker/crab2.jpg[/IMG] [IMG]http://i226.photobucket.com/albums/dd7/Coralmaker/crab1.jpg[/IMG] bob <<Two really great shots there Bob, and they will certainly be welcomed into our picture database. Thank you very much for providing / sharing two wonderful pictures. Kind Regards, A Nixon>>

Pom Poms and Croceas 9/9/08 Hi there guys, I have a nano 10 gallon with a 175W Metal Halide on it. <"Giant steps are what you take, walking on the moon/sun"> It has a 2.5 gallon sump/fuge with mangroves growing in it. 14.5 pounds live Rock, 10 Pounds Live sand, assorted sps and LPSs plus Zoos and Palys, Established tank, 9 months old. Ok, so my question is this. Stinging corals, especially LPSs, can harm clams very easily if they get too close. But can anemones do the same? <Yes> More specifically, I want to get a pom pom crab because I think they are very interesting, and well, just plain cool, but would this Crab hurt my clam. My porcelain crab and my emerald crab both love to climb over everything and make a mess. Could this be problematic with a pom pom and a clam? Thanks, Andrew <Some chance, but most Lybia avoid the mantles of clams... The real issue here is going to be "just size/volume"... When, not if, "something" goes awry here, there is going to be very little "wiggle room" or reaction time to prevent a complete melt-down. Bob Fenner>

Re: Gaudy clown crab 4/16/08 Thank-you for replying. Today our shipment of live rock arrived of 85 pounds. When we were done placing it all in our aquarium we tried to get the gaudy clown crab out but it was wedged so far into that one rock it didn't make it. <Sometime later then... baiting, trapping...> Later on tonight we were looking and in the corner of our eye we noticed a second one. Now is it safe to keep in our aquarium?? Or should we put it in another tank? We have fish and shrimp and blue legged hermit crabs etc. Please reply and let me know thank-you <Please read here: http://wetwebmedia.com/swcrabcomp.htm and the linked files in the series above... till you understand your options sufficiently. Cheers, BobF> Re: Gaudy clown crab 4/16/08 I looked on that site that u <...> gave me there was nothing on there about gaudy clown crabs. Im sorry to be bothering you again its just no one around where I live knows anything about them. I would be grateful if you helped me know more about the gaudy clown crabs. <... Please read generally re the Compatibility of marine crabs period... B>

Mystery Crab: Possible Xanthid - Cute But Not Reef Safe - 1/21/08 Hello <Hi Lisa!> I was hoping you could help me ID this crab: <Will sure try!> http://i61.photobucket.com/albums/h61/coppersunflower/IMG_0443.jpg http://i61.photobucket.com/albums/h61/coppersunflower/IMG_0449.jpg It came into my tank hiding in a rock I recently purchased. It is quite small (less then a half inch), is white in colour and appears furry. I've found nothing that resembles it online. <Heeeee! I don't know what's going on, but suddenly everyone's asking for crab ID's! Hmmmm, note to self: Write article for WWM titled: 'Guidelines for Successful Crab Identification'! These little guys can be notoriously difficult to ID. It's all in the details! Each family/genus (not to mention: species) has its own set of distinguishing characteristics. Sometimes they're very obvious and easy to differentiate, sometimes not so much. As far as I can tell, the little crab you have is a Xanthid (family: Xanthidae). These are cute little guys when small, but can grow to be a real problem later on. I would not consider it reef safe and would relocate. Please see these links for more information re: http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabs.htm http://www.reefkeeping.com/issues/2003-12/rs/index.php .> Any help you can provide would be greatly appreciated. Thanks Lisa
<You're very welcome! Take care --Lynn>

Stylophora pistillata hitchhiker: Xanthid crab? - 1/20/08 Hey folks! I've got a crab ID request if you have a moment. <Heeee...these often take many 'moments', but they're always great learning experiences!> I found a very small (~1/4") juvenile(?) reddish-brown hairy crab munching/pruning on a Stylophora pistillata frag I just purchased. <Yikes, was there any apparent damage?> Distinguishing features include bushy hair everywhere (body, legs and claws), green eyes, orange claws with white spots and white tips. The body has white spots as well. <Well, when you mentioned Stylophora, I was hoping that this was a little commensal crab in the family Trapeziidae. The general shape and coloring are right on, but I've never seen anything in this family that was so hairy. I've seen some with spiky hairs on the two rear legs, but never all over. I'm not sure if your little crab is hairy because it's a juvenile, or because it's a different family/species altogether. I'm more inclined to think that it's the latter. If it's not a Trapeziid, it's likely a Xanthid, and potentially destructive. Not all Xanthids have dark claws. There are also plenty of species that are hairy, and they're known to sometimes hitchhike into our tanks within the branches of stony corals.> I have removed and sequestered the crab. He was very good at remaining motionless when approached, hugging the coral. Pretty good camouflage against the brown branches of a brown/green Stylo! <Typical. Small creatures like this need all the help they can get when it comes to avoiding predation! Their ability to blend betters their chances of survival.> Enclosed is a picture. Sorry for the poor depth-of-focus. I would like to know what this crab is, and whether or not it will be a good citizen in my 55g. <Hmmm, wish I could be more help here but unfortunately, after looking everywhere I can think of, I can't confirm anything. I'm sure you know the general rule of thumb that keeping crabs in a reef tank is a risk. Even commensals can cause problems if they get hungry enough. Thankfully, that risk is reduced by virtue of the fact that most commensals stay fairly small. I'm leaning more towards this little crab being a Xanthid. He/she might be okay for a while, but not knowing which species it is, I don't know how large it can get. I'd take a good look where this little crab was 'munching/pruning' on your coral. If it's damaged, you've got your answer. If not, it could go either way. If you decide to return it to the tank, just keep an eye out for problems/damage, and trap/remove if necessary.> Thanks so much for your time! -Scott
<You're very welcome, and good luck! --Lynn>

Crab ID Needed -- Acropora Commensal! 1/19/08 Hey, guys and gals -- 3rd letter this week! <Yay! What can I do for you today?> I bought my first piece of Acropora coral and I was pretty excited. <Understandably so, they're beautiful corals!> Well, guess what? A little buddy hitchhiked his way on the coral! He's pretty much all off white with a bit of blue-ish purple on his shell. <Yep, I've seen this little guy's kin before. They're neat little crabs.> He looks nice and was snuggled in the branches of the Acropora frag but I have no idea if he's a good guy or bad guy. If he's bad, I would guess it'll have to be the sump for him until my refugium gets built! Here are some pictures to help with the ID. Hope they are clear enough! <They are, thanks! I'm happy to say that this little crab is a keeper. Ninety-nine percent of the time, when people write in about hitchhiking crabs, we have to warn them about the potential risk to their livestock. This, however, is the one percent that makes for an exception. What you have is a little Acropora (commensal) crab, in the genus Tetralia. They stay small, and are actually good for the coral. Interestingly enough, in the wild, this crab protects the coral from the voracious Crown-of-Thorns sea star (Acanthaster planci). It pinches the tube feet of the star and "discourages" it from dining on the coral! I have a link for you to read through for additional information, as well as several others with photos: http://www2.hawaii.edu/~delbeek/afmjan97.html http://home2.pacific.net.ph/~sweetyummy42/hitchcrabs.html http://home2.pacific.net.ph/~sweetyummy42/coral_crabs-2.html .> Thanks, Jon <You're very welcome. Enjoy your new additions! --Lynn> Jonathan Philpot

Hitchhiking crab -- not a good risk 1/18/08 Hi Guys <Hi Lesley, Lynn here this afternoon.> Hoping you can be as helpful as you usually are! <Hope so!> I purchased some live rock today, just to better aquascape the tank. Put it in, popped out for a few hours, and when I got back, there was this little bugger sitting there looking at me! <'Yeah, that's right, I'm a crab...see? I'm going to wait till dark then eat all your little fishies...see?' Heeee. for some reason, I've always imagined that if crabs could talk, they'd sound like Edward G. Robinson. Ever see that old movie, Key Largo, where he played the gangster Johnny Rocco and - umm, never mind. :-)> He was easily caught, not very shy, and approx three inches across. <Fairly large for a hitchhiker -- they're usually pretty small, and shy.> I've managed to trap him in a breeding trap until I know if he is reef safe or not (mind you, if he's not, what do I do with him!) <Well, there are a few choices: set him up in a separate tank, call your local fish stores/where you got the rock, and see if they're interested in him, or, if you have online access to a nearby fish/aquarium club's forums, you can post there and see if anyone wants him.> I've been all over the site and can't find anything that looks like him, so do you guys have any ideas? <Well, I'd need a photo from the dorsal/top side to get a better idea of what family it's in, but the bottom line is that crabs are not good candidates for reef tanks. This is especially true for larger crabs. Large crab = large appetite and increased risk to resident fish/other invertebrates. I'd find this guy another home, either in a separate tank at your place, or elsewhere. Please see these links for more information re: http://www.reefkeeping.com/issues/2003-12/rs/index.php http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabs.htm.> Kind regards Lesley <Take care -Lynn>

Re: Hitchhiking crab -- not a good risk 1/18/08 <Hi Lesley!> Many thanks Lynn, I don't know what I'd do without this site! <You're very welcome. As always, it was a pleasure! Take care --Lynn>

Crab Removal and Tuxedo Urchin vs. Soft Coral -- 12/13/07 Good morning, <Hi David!> I'm curious about the jar method for catching crabs. I took equivalent of a pop bottle, carefully peeled off the label and scraped off any adhesive... Then I boiled the bottle in a pot to sterilize it for 5 min.s. Once cooled down, the bottle was perfectly clean and hopefully sterile. I filled the bottom with about 3" of sand and placed 3 pieces of krill in it... The bottle is leaning up against the crab infested rock...48hrs... No crabs trapped. <Takes time, patience, right bait, and hungry crab(s).> The largest crab could fit into the bottle opening sideways. Do you think I'll have better luck if I use more sand to bring the bait closer to the neck of the bottle? <Can try this, as long as the sand isn't up high enough to allow the crab to grab the top edge of the bottle and crawl out. One possibility is that the krill just might not be 'stinky' enough to lure him/them in. It sure would have been nice had the crab(s) gone the easy way and fallen for the jar trap! Since they haven't, and it sounds like the crabs are all still fairly localized, I'd consider removing the rock to a bare bottom quarantine tank and thus gaining the upper hand. One of the many good things about this is that you can control the food supply. When he/they get hungry enough, they'll go after whatever's in that trap. It also eliminates the possibility of your other inverts accidentally wandering in. The main advantage though, is that the crabs can't wander off and take up residence elsewhere in the display before you catch them!> This morning I spotted the large crab likely about 4" away from the Jawfish. <Hmmmm> The Jawfish didn't seem concerned and the crab was feeding on some Caulerpa. I have had emerald greens before without incident (mind you none were this big)... This crab looks identical to the emerald green Mithrax, except it is black with sandy brown legs. Would you say that any crab that's of decent size is likely risky in a reef tank with smaller fish? <Yes> He is kinda neat, but obviously I don't want to stumble upon a Jawfish carcass one morning. <No kidding!> If the 'jar method' for catching these critters takes too long... Do you think removing the liverock and placing in a bucket of tank water and putting some powerheads on the holes would drive them out into the bottom of the bucket without damaging the feather dusters and soft corals? <You could give it a try, but I'm thinking it's more likely the crab(s) will simply hunker down/go into an area of the rock that's not getting blasted. There's also a good chance that it could damage those soft corals. My next step would be as stated above: QT, control food, trap/net.> I have a fairy wrasse in quarantine and I suspect the wrasse will find this crab infested liverock that is so porous with a variety of large chambers within... Of particular interest for a home. Sleeping wrasse in liverock infested with a few small crabs and one brute... Ok, maybe I am answering my own question. Could be disaster? <Heeee! Yes -- something along the lines of 'Come into my parlor, said the spider to the fly!'. Depending on the size of the wrasse, you might be able to block off/separate part of the QT with Eggcrate, or similar.> Lastly, I mentioned my small tuxedo urchin sitting in my soft coral tubular polyps. I believe he was just passing through. You had mentioned I should move him. Anyhow, when I came home from work all the polyps were open and no apparent damage and urchin seemed ok as well. This is two days later now, again last night Urchin was sitting in the polyps again. <Hmmmm> I'm wondering if you figure he's once again just passing through or... Can/does an urchin actually feed on corals? <According to what I've read, Tuxedo urchins/Mespilia globulus, rarely eat corals. They're mostly herbivorous, but if they ran out of algae/got hungry enough...? I'm a little concerned, about the repeated visits to the soft coral -- unless it's dining on algae on the base/where it's attached. Would monitor closely for any signs of damage.> Anything I've read suggests they are totally reef safe. If no damage is being done I'd like to keep both... The alternative is to move the tuxedo urchin to my 200g FOWLR tank that houses a Snowflake Moray, Foxface, Harlequin Tusk, and soon to have tangs/Angel/trigger.... <Would monitor, relocate if necessary.> David Brynlund <Take care - Lynn>

Dragonet and Sally Lightfoot Crab 12/1/07 Hello, I love your site and thank you in advance! My question is regarding a Sally Lightfoot Crab and my Dragonet ( a scooter blenny or perhaps a starry blenny). The dragonet is slow moving and just kind of "hops along" the tank and rock work. Will my newly purchased Sally Lightfoot be able to catch him and/or is he a threat to him? <Yes it can. Although it is not a guarantee that he will.> I heard from my LFS salesman that my dragonet is poisonous to eat displayed by the bright colors. Is this true and will that deter the Sally Lightfoot? <They are somewhat thought to be. Do not trust that particular crab (and several others) in with such a small, slow moving fish.> Thank you -M. Allebach <Welcome, Scott V.>

Seahorses and crabs 10/16/07 Hi. I recently purchased a pom pom crab. He is ready to come out of quarantine. I was planning on putting him in my reef tank, although I have a Rolland's damsel that is becoming aggressive and may have just killed my strawberry crab. I witnessed the damsel attack the strawberry crab the other day. The crab got away quickly, but this morning I found him laying dead in the sand and am wondering if the damsel is to blame since the crab seamed otherwise healthy. Plus the new crab is so tiny that I doubt I will ever see him again in a 55 gallon tank. <Too likely so> I also have a 20 gallon tank with two young h. erectus. Would it be safe to house the pom pom crab in the seahorse tank? <Mmm... a better choice than with the Rolland's...> I know that anemones and seahorses do not mix, but will it matter when they are so tiny? Is there any way the pom pom crab would hurt the seahorses? Thank you all so much for your help. Your website and helpful expertise are a blessing! -Connie <Thank you. I would take the risk here myself with the Seahorses. Bob Fenner>

Random questions/reef tank... maint., crab comp., Zoanthid contr. 9/26/07 Hello all and thanks for the great website! I hope this is not too annoying an e-mail, but I have several somewhat unrelated questions that I hope I did not miss the answer to in the FAQs. We have a 90 gallon reef, 4 inch DSB, 120 pounds live rock, with the following livestock: Naso tang (N. lituratus), <This genus, species needs more room than this... as stated on WWM...> pair of Clarkii clowns, mandarin dragonette, double-barred Rabbitfish, yellow tang, cleaner shrimp, peppermint shrimp, and sally light foot crab. It's the dreaded "garden reef" <Heee!> with predominately SPS in the upper third and LPS in the bottom half. However, just to cause trouble, we have three different types of Zoanthids and two types of mushrooms. We have a protein skimmer and run carbon. No new fish or invertebrates have been added in over six months. Thus far, all corals appear to be flourishing and all fish are happily coexisting. Don't panic over the stocking..... we are in the process of upgrading to a 220. The tank is finally in and husband is installing the floor jacks tonight! Parameters are: ammonia/nitrate/nitrite/phosphate-0, SG-1.025, pH-8.1, temperature-81, calcium-450 mg/dl, and alkalinity-8.5 dKH. So, on to the myriad of questions......1. The Rabbitfish has developed a pink hue on both lateral sides just dorsal to his abdominal area. I have not seen this in any picture of a Rabbitfish, but perhaps it's just too subtle for pictures. Is this something to be concerned about? <Mmm, yes... highly likely environmental/stress caused... will abate with the move to larger, better setting> Fish is eating fine (varied diet of Mysis and other frozen seafoods, Nori, flake, pellets, etc.) and acting the same as always. 2. I inquired about a final fish to the stocking plan and EricR had suggested a powder brown tang. We weren't crazy about the tang when we looked, so what are your thoughts on a Sargassum triggerfish? Do you think the odds are good that this would be a reef safe fish (no guarantees we realize) and that this an appropriate addition to a peaceful tank? <Are good animals for larger systems... and not too adventitious as other Balistids... May still sample your cnidarians> 3. The yellow Zoanthids (Parazoanthus gracilis I think) have gone absolutely out of control. We started out with a small rock with perhaps 5 polyps on it over a year ago and we know have hundreds of polyps. They have grown through the rock to come out in different areas. <... got to keep them isolated... on their own patch of rock...> When we try to prune them, one polyp always seems to escape and then a new colony starts wherever it lands! They are growing across the sand bed, in the back of the tank, and even in the middle of other Zoanthid colonies. Any suggestions for curbing their growth? <Remove as much as you can in the move to the larger tank> The main polyp area is on a huge rock that supports a lot of the other rock structure, so removal is not possible....well not easy anyway. At first they were quite pretty, now they remind me of dandelions on a manicured yard! 4. Last question and most important....any hints for trapping the sally light foot crab!?! <Box traps... you can buy as such or just the plastic ones for small rodents (they're the same)...> Last month I walked by the tank to see the crab eating one of the cleaner shrimp (Arrgh, the horror...I tell myself the crab was merely scavenging, but....). <Ah, no> Last week the yellow tang had a tear in the caudal fin. The fin healed, but we are worried the crab is on the prowl. We have tried physically grabbing the crab (yeah, no shock that didn't work) and commercial traps which resulted in one trapped and very stressed clownfish. When we put frozen fish in a jar or on a string to bait the crab, all the other fish grab the treat. We have tried feeding the fish on the other side of the tank at the same time, but they are too clever for that! Assuming we catch the crab, can we just place him in the fuge or would one crab defeat the purpose of the fuge, especially since we rely on the pod production for the mandarin? <Move, isolate, trade in with the move...> Thanks for the help as always and sorry for the long e-mail. All of you do a great service to us newbies out here! Michele <Congrats on the new, larger system. Bob Fenner>
Re: Random questions/reef tank 9/26/07
Thank you for the reply. Yes, we know the 90 gallon is WAAAY too small for the Naso which is why we are upgrading to the 220. We didn't do our research when we bought her last year, but we are trying to make it right with the new tank. <Good... I do hope you get on out to the wild... see these active fishes there> The tank was a custom order this past January right after we got the Naso, but it only finally got here last month! We had certainly hoped to have her in the larger tank sooner than this. You have me quite stressed now that the Rabbitfish's coloration is secondary to the small tank....we shall try and get the new tank up and running quickly! Michele Frazer, DVM <Do please send along an image or two when it's settled in. Cheers, BobF>

Crab and Candycane comp. -- 08/27/07 Hi Crew, Yesterday I noticed something on my Candycane. In between the outer brown and the inner green it looked like something got caught on there. So I took a tweezers and it lifted right out but it came out swinging. It is (was) tiny and I doubt if I could have presented a good picture. I usually let things, that I find in the tank, live. But my gut feeling was that this was a bad guy, at least for my Candycane, so my tweezers crunched the perpetrator. It looked like a miniature crab. I do not recall reading about any Candycane pests. I have this candy cane a couple years. But recently I took in a large colony from someone since it was deteriorating in his tank. Maybe it is infected with this pest. I have not found any more yet. Right now the bright green center of the head that had the crab does not look bright and is not very green. The mouth is a large hole and is how many of the heads look in the colony that I took in. Aside for keeping my eyes open for more of these creatures is there anything I should do? Would it be useful to do a freshwater dip to force out any more of these creatures? <Naw, don't do that. It won't help and would probably just stress out the coral.> I did not quarantine the sick Candycane because it came from a tank that is much better than mine and my thought was that the other corals were causing it to decline. <Well, quarantining has nothing to do with how well the tank it came from is/was doing. But anyway'¦ very few crabs reproduce readily in aquariums. So even if this 'crab' is a pest, if it's actually a crab, I wouldn't worry about it multiplying. Also, you never know if the crab caused the coral's problems or if it simply took advantage of the coral's decline. Just keep an eye on the coral. If it doesn't recover, then you might have to think more about why it's suffering.> Thanks <De nada, Sara M.>

Added Crabs, Shrimp are Gone; Mithraculus 8/22/07 Hey gang! Boy, if anybody can mess something up it's me. <I bet I'm worse.> I had/have an issue with Valonia (sp?) bubbles, it was really severe. I decided against the raccoon butterfly because of issues it might have with my inverts so I bought some small Mithrax crabs.. <Ok> The Valonia bubbles are receding except for the big ones I can snag with a siphon tube but what disturbs me is the sudden disappearance/deaths of my shrimp. <Uh oh> In the past two weeks (since introducing the crabs) I've lost two very large skunk shrimp and one small peppermint shrimp. I took the deceased peppermint out, it seemed to be intact. I only saw the carcass of one of my skunk shrimp briefly this morning but it was gone before I could get it. No sign of the other. <Dead things disappear very quickly in aquariums.> Everything else in the tank (2 fire fish, 1 azure damsel, 1 royal Gramma, 1 orchid Dottyback, and assorted corals that have been in the tank since I started over a year ago plus one huge bubble tip anemone and it's large clown) are fine. Is it safe to assume that the Mithrax have killed the shrimp? <Definitely a possibility> I wouldn't have expected it, I figured they'd feast on the bubbles. <They eat whatever is in front of them.> Should I trap and remove them? <Could> I have a large abalone I'd hate to lose but I am seeing some empty snail shells as well. <Sounds like the crabs may be your problem but hard to say for sure. If something else is killing the shrimp and snails then the crabs may just be cleaning up the leftovers.> Thanks for your kind assistance that you generously offer. Lisa <If possible separate the crabs into the sump if you have one or another tank and just move live rock in and out as they eat the algae.> <Chris>
Re: Added crabs, shrimp are gone! 8/23/07
Thanks Chris :) I'll set a trap tonight. I do have a refugium, it's full of Chaetomorpha. I'll add some rock. <Sounds good.> I watch the tank at night with a red light, the only thing I notice are the crabs. I'll update when they're out. <Ok> Thanks so much for all you do :) Lisa <Welcome> <Chris>

When In Doubt...(Potential Problem Crab) -- 08/08/07 Scott, <Scott here, Captain...> Since I have your attention . . . what's your best guess on an ID of the attached crab and whether I should try to get him out of the display? Looks to me like a Mithrax forceps. So far, he does not "seem" to molest any of his tank mates. I will say, however, that the dorsal fins of my Maroon Clown and Brown Combtooth Blenny do sometimes have "chunks" taken out of them (which quickly regenerate). Andy <Well, I'm not really well versed on crustacean identification (that kinda rhymes, huh?), so I would probably err on the side of conservatism and consider removing the crab to a tank of his own where the potential to cause trouble is not there. I've made the mistake of not following my initial gut feeling about things like this in the past, and paid the price later! It may very well be harmless, but my philosophy is "when in doubt, take it out"! Best of luck! Regards, Scott F.>

Shrimp vs. Crabs: Overcrowding/mixed species issues - 7/24/07 Hello, <Howdy> I have been puzzled over the last few weeks and I am hoping you all can help. <Hope so!> I had a fire shrimp and two cleaner shrimp in my tank and they seemed to be thriving. Very active, the fire shrimp molted several times, and was a brilliant red. <They really are beautiful shrimp> Well, about 2 weeks ago, one of the cleaner shrimp had died, or been killed, and my sally lightfoot crab was eating it. <Sorry to hear that> I figured just bad luck. <More likely a hungry crab> About 1 week later, I added another <!> sally lightfoot <Houston, we have a problem> and within two days the other cleaner shrimp was dead and being eaten by the crab. <Yep, saw that one coming> I started to be concerned, and took some water to the LFS to check it out, and everything thing came back in great range (I'd list it all, but I don't have the exact #'s with me)<Okay>. This morning I awoke to my arrow crab <Yikes! There's an arrow crab in there too?> and sally lightfoot eating the presumably dead fire shrimp. Now these guys are <aren't(?)> the cheapest things in the world, and I <I'm> wondering if I should buy another one, or not, with the crabs in the tank? <Definitely not!> I have 2 sally Lightfoots, 1 emerald crab, 1 arrow crab, electric blue hermit crab, and a couple Cortez hermit crabs. Is it bad luck <It's more than that> or are they praying <preying> on the shrimp when they molt? <Possibly, but I'm guessing they just like shrimp.> Tank is a 14 gallon bio cube, with a few small corals, 20 lbs of live sand, and 14 pounds live rock. There are some mushroom colonies, a small clown, and purple Pseudochromis. <I'm sorry for your losses, but unfortunately, the issues here are: too many different/incompatible shrimp/crab species, in too large a quantity, in too small a tank. If you want to keep shrimp, I wouldn't put more than a single specie in a 14g BioCube, and no crabs. Crabs in general are not a good idea in mixed reef situations, much less in high concentrations. Sally Lightfoots and arrows, in particular, are known to kill small to medium fish and invertebrates -- pretty much anything they can get hold of. Emerald/Mithrax crabs can go either way, IME. Sometimes you get lucky, sometimes you don't. While it's possible that the actual deaths of the various shrimp could have been due to other factors (stress of overcrowding, starvation, etc), it's most likely the crabs did the killing. I would decide on keeping one or the other, and trap/return the rest. I would also recommend reading the FAQ's, and info at WWM re: keeping/compatibility issues for these species, and prior to any future additions. http://www.wetwebmedia.com/marine/inverts/arthropoda/shrimp/cleaner.htm http://www.wetwebmedia.com/swcrabcomp.htm http://www.wetwebmedia.com/arrowcrabfaqs.htm Good luck!-Lynn>
Re: Shrimp vs. Crabs: Overcrowding/mixed species issues - 7/25/07
<Hello!> Wow, you guys/girls are awesome, thanks for the information and the advice. <You're very welcome and thank you for writing in! Although it's too late to save your little shrimp, your shared experience could save others down the road! -- Lynn>

Stone Crabs! - 7/18/07 <Hi Bridget!> I have pulled 3 of these guys out of my tank in the past 6 months. <Yikes!> Pet store ID'd the last one and advised an elimination program. All research on the web tells how tasty they are. <I've never had them, but I've heard that as well.> That really is kinda useless. <Well, if you do indeed have the same variety of "stone crab" that they use in the seafood industry, you can try Googling its scientific name: Menippe mercenaria. That's the problem with common names, though. One name can be used for many species.> My biggest question is, are they really all that bad? <Well, not if you want a crab tank! If you want a reef tank with snails, etc, in it, then yep, I'm sorry but they're bad. Crabs in the Menippe genus are Xanthid, or mud, crabs and have a bad reputation for being destructive in reef tanks. Also, some Xanthids are toxic, so just in case, don't let anyone eat those crabs!> If so what's your best advise for removal? <Please see this link and the post labeled 'Trapping in Displays': http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabfaqs2.htm > I do know I no longer have any hermit crabs and my yellow tang has gone missing? <Hmmmm, not good.> Now have 3 fish in the 75, 2 true Perculas and one coral beauty. Thank you for your time Bridget <You're very welcome, and good luck! -Lynn>
Re: Stone Crabs! Follow-up 7/19/07
<Hi again, Bridget! Lynn here.> Well I found some pictures here http://www.okeefes.org/Crabs/crab%20photos%20and%20scans.htm and this guy <(Pilumnus sayi)> is definitely what I have and not the stone crabs <(Menippe mercenaria)> *Pilumnus sayi* <Thanks! Pilumnus sayi, sometimes called the hairy mud crab, or spineback hairy crab, has those same robust claws as the yummy stone crabs (Menippe mercenaria) but with lots of bristles! Unfortunately, it's still a Xanthid and potential trouble down the road for a mixed reef tank.> Hubby is being a grump and not wanting to remove these guys. <I can understand that. As much trouble as they can cause for the other inhabitants of your tank, they're still neat little creatures! Why not set up a separate tank for them? It's a win-win!> Myself, I'm more than concerned about the quantity and I'm wondering if they might be reproducing or if they just came in with the live rock. <Almost guaranteed that they came in with the rock. The juvenile stages of crabs have a next to nil chance of surviving in the average tank.> I don't see these guys. They're professional hiders, <Yes indeed!> I'm only finding dead bodies. <Of snails, etc, or the crabs themselves? If it's snails, etc, that's not too surprising. If it's crab bodies, they could just be the shed shells from when they molt.> Which makes me more concerned about anyone else in the tank. <Understandable either way!> Tank is a 75 reef established 3 years, new live rock with oysters 6 months ago. <Sounds like a nice tank to me!> Thank you for your time. Bridget <You're most welcome, Bridget. I'd try to trap these guys (see previous link on this) and set them up in a tank of their own. Good luck! -Lynn >
Re: Stone Crabs! Follow-up: Mysterious losses - 7/19/07
<Hi Bridget!> These are definitely dead crab bodies. I've had several crabs/shrimp that have molted and it's fairly easy to tell the difference. <Yep, sorry about that. I figured you probably already knew, but wanted to be sure.> I saw the last one the night before hanging upside down on the rock and he was a pinkish red color which told me he wasn't feeling good. Next morning he was sitting on the bottom of the tank. I had to really fight to get him loose. He'd latched onto some plants, and a rock, and wasn't wanting to let go. <The loss of these little crabs may be a simple matter of too much competition for food. By the way, if you have any shrimp, have they been shedding normally? If not, you might want to check the iodine level. Insufficiency here could explain some of the other invert deaths as well.> I still have the whole body sitting here in a jar in front of me so I can reference back as I'm searching. My biggest concern was reproduction. <No worries there. True crabs, such as yours, hatch into a planktonic zoea/larval stage that, without special food/care, have very little chance of survival in a tank. They drift along in the currents, and become part of the food chain.> Now I'm going to set up the pickle jar tonight. After doing the reading I started searching the tank for lost residents, 3 queen conch, 12 hermits, and about 20 odd ball snails, missing. Past 6 months or so yellow tang, purple fire fish and blenny have disappeared. Crabs need to go.. huuummmm <Yep, that's a lot. If water parameters and chemistry are/have all been fine, and there's been no apparent disease/injury, and finally, there's been enough food for all those inverts, then you have to consider predation. I'd definitely put a trap out and see what you get. Just out of curiosity, have you heard any popping or clicking sounds coming from the tank, especially at night?> Reminds me, walked into the fish store and told them I had crabs. You can imagine those poor young men trying to keep a straight face. LOL <LOL!! They're probably still laughing over that one! I know it'll keep me going for a while!> Thank you Lynn for all your help Bridget <You're very welcome, Bridget, and thanks for the laugh!>
Re: Stone Crabs! Follow-up 2: Mysterious losses - 7/19/07
<Hi Bridget!> No strange noises, but we turn off the tank and go to bed. Will let you know. <Sounds good.> You've been great. <Happy to help - I just wish I could have been more so!> Water is good, corals, mushrooms and anemone are growing and healthy happy. <Terrific!> Thanks so much Bridget <It was my pleasure! Take care --Lynn>
Re: Stone Crabs! Follow-up 3 - 7/20/07
<Hi Bridget!> Nothing this morning, will change location, feed less at dinnertime and shrink the jar a little and try again. <Yep, trapping can take some time/patience/luck. Using 'stinky' bait (shrimp/squid/etc), should help.> Hubby seems to think that we may have lost some of the crew with the spike from the new rock, it's a good sized rock, 35lbs <Yowza! It's entirely possible, especially if it wasn't cured. Even if it was, though, it still would have caused some chemistry changes.> with 7 oysters on it, <Neat> one tunicate that I adore, he's about 3" tall, bright orange. <Pretty!> We got the oysters for added filtration, and they are reproducing rather quickly. <Sounds like they're happy!> It also came with some non photosynthetic stony coral on it, it came with 3 polyps on it and now there's six of them. <Nice!> Also have something that looks like it might be a baby bubble tip. Except it has this long curly tongue kinda thing that hangs out, when hungry. <I've got a dog that does that when he sees ice cream.> Cream and pink colored about 3/4" around and impossible to photograph through that thick glass. <Understandable, that can be a challenge.> Will update again as soon as I have any news <Please do!> Take care <You too, and have a great weekend! --Lynn> Bridget

Please help!! Clown and Crab Interaction 7/13/07 Good Afternoon guys (and gals), <Hello> I have a 10 gallon FOWLR (&LS) set up with a Skilter skimmer, maxi-jet 600, and very stable readings for two weeks straight after cycling for 5 weeks. <Ok> Last night I added a false Perc and a sally (she was a throw in from the person I bought my Perc from). After using the drip method for acclimation I have noticed that my false stays on one side of the tank and the sally roams free. <Not unusually for a clown, although you want to watch him closely.> I think I noticed (could be paranoia) the crab stalking my clown. <Possible> I think its nothing more than paranoia but I am really getting worried about the crab trying to attack my Perc. <Crabs eat whatever they can catch, and Sallies have been know to catch small fish.> He is constantly looking for her and it appears to be scaring my clown. I looked on DFWMAS.org and I got differing answers....I am about 99% certain I have nothing to fear but after reading up on my totally unexpected and unprepared for sally it appears he wont be in my tank for long regardless. <Probably the best move.> I guess my question is whether or not I should be concerned with the sally eating my clown. <Can happen, although not too often.> Other than looking totally freaked out whenever the crab "appears" from the rocks he/she is doing great and eating. I see no markings on (we'll go with her) her and she is very active.. albeit on one side of the tank. Thank you in advance for you help Phil Murphy <Welcome> <Chris>

Hitchhiker Crab Removal - 6/7/07 Hi Crew, <Hi again, Debra!> I have found another crab hiding in my sun corals. <!> I don't want to ID him, I've seen enough of him to know I don't want him around, period. <Heehee, does this one have beady eyes too?> But flushing him out won't be as simple. The first one slipped into a small rock which was easily removed and exposed to air. Once exposed to air, within a few minutes he was out where I flicked him into the water using a bamboo skewer and removed the rock. But exposing my sun corals to air for any length of time to try and flush out this crab would most likely cause them more harm than the pesky crab is causing. If left alone at some point he will get too big to hide in the sun coral and seek another home. Are we talking months or years before Dennis the Menace becomes Ivan the Terrible? <Sorry, too many factors to be able to make a call here.> Should I just resolve the fact that there's not much I can do until it gets bigger and go ahead and move my sun corals from quarantine into the main tank? <I wouldn't. That's one of the great things about having a QT (and good for you for using one!). If you want to get rid of this guy, now's the time. If you wait until he's in the display, he'll be even harder to catch. It could take some serious aquascape rearranging, and frustration, to get him out of there. Plus that, chances are that by the time you want him out, he will have already done some damage. It's just not worth it.> The main tank (20 gallon long) is still in the building stage so there are only 2 other sun coral colonies, one Tubipora musica and two cleaner shrimp (L. amboinensis). Fish additions are still being researched <Love to hear that!> but currently I have in mind one Royal Gramma and 2 Pajama Cardinals (or 1 cardinal). <Okay> Should I just plan my tank around the fact I have a crab and set a trap nightly until he's caught? <Again, I'd remove the crab now, while in quarantine. One thing you could try is flushing it out with a turkey baster (with the coral submerged). Remove the sun coral to a bucket with some tank water (enough to cover). Using the turkey baster, 'swoosh' water directly at the little crab (underwater) until he gives up and runs out. Just be sure to aim the blasts below/between the polyps. It may take some doing, but it should work. Sounds like you're already proficient with bamboo skewers, so one of those might come in handy as well to prod him out. If that doesn't work, see here for more information/ideas on trapping: http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabfaqs2.htm> What should I be wary of adding to my tank because of the crab? <Will no longer be a factor once he's removed, but crabs are generally opportunistic - can go for just about anything.> Having done some research on this site: http://www.imv.uit.no/crustikon/Decapoda/Decapoda2/Species_index.htm, which has a lot of pictures of various crustaceans, I think it might be in the Xanthidae family based on the similarity of its body shape. <Mmmm, yes, this group contains a lot of crabs that can be a problem in a mixed tank.> Thank you again. Regards, <You're very welcome and good luck! -Lynn>

Hitchhiker Crab Removal - 6/7/07 Hi ...Lynn? <Yep, hi Debbie. What's up?> During feeding my sun corals tonight I was able to flush out that little critter using a bamboo skewer with the tip bent at 45 degrees. <Heheee! You really are good with those skewers!> I accidentally broke off one of his legs during removal and the one you see fell off while it was walking around the container (probably because of me). <Will grow back.> In case someone else runs into the same thing, here's a picture of him with one of his missing claws. <Appreciate it, and thanks for including the dime for size reference.> Curious, is it in the Xanthidae family... can you tell? <Sure does appear so to me.> I'm not positive but I think both claws were identical, pictured is the left claw. Although looking brownish here it is actually more of a maroon color. Hopefully there will be no more crabs on the coral, but back to quarantine to be sure. <Good for you - keep your eyes peeled and a skewer handy!> Thanks for all your help. Regards,
<You're very welcome! --Lynn>

Re: Red Fromia star has hole in its head! Help! 4/4/07 Mich, Thanks for the reply. <Welcome!> The star ended up dying. <I'm sorry for your loss.> I believe it to either be an acclimation issue OR the teddy bear crab. <Either are possibilities.> I went back to the shop where I had acquired the star and there was a star from the same batch that disintegrated also. <Unfortunately this is not terribly surprising.> But, to my horror, I caught the teddy bear crab eating my sand-sifting star the next day! It ate a whole arm before I knew what was happening. <Yikes! I would not recommend the sand-sifting star (Astropecten spp.). These stars decimate your sand bed removing beneficial organisms and typically starve after a few months in captivity.> Needless to say I have removed the teddy bear crab from the tank. <Mmm, hopefully to a suitable home and not an untimely demise.> I had searched online about the teddy bear and various sites said it was reef safe and a detritus eater so I thought it was safe, thanks for the info that says otherwise....wish I would have known. <Not every source hold equal value.> Hopefully the star will live and regenerate a new arm. <It may.> Unfortunately, none of my corals are happy since adding the sponges. The tank at the store that one of the sponges was in was being cleaned when I bought it (water was really cloudy). I'm starting to think that I introduced a lot of toxins since I had to introduce that water into my tank. <Yikes!> I am going to do a few water changes daily for the next few days to get any toxins out. <Do watch this carefully. Dying sponges can really do a lot of damage.> Green mushroom won't open up, gorgonian won't come out and my torch is losing tentacles! <Ho buoy! Not good!> I'm about to do a water change right now. <Good!> I changed it yesterday and the gorgonian came out for a while. <You may need to do several large changes here!> Wish me luck! <Good luck my friend!> Thanks again for the info, <You are most welcome! -Mich> Luis

Hermit's a tripod now??? 3/11/07 I have recently noticed that one of my larger--actually the largest of my red tipped hermits has lost many of his legs. <So the Vietnam was is raging in your tank?> He currently only has his pinchers and one left leg. He is unable to walk or climb. The only thing that he can do with seemingly great difficulty is turn in a circle. <This is to be expected with a Septa-plegic.> I have been hand placing food in front of him for the past couple weeks to prevent him from starving. <As long as he is eating it, and you can continue this, after a few molts, the crab should start to grow new legs.> All of the other hermits are fine. -----Is it normal for this to happen to this degree? <It is never normal for inhabitants to start losing limbs. The Sally Lightfoot that you mention below is a likely culprit. Actually, if you have a refugium, or another fishless tank to put this one in, I would do that. Eventually you will be E-mailing us wondering what ate your fish. The answer will be the Sally Lightfoot.> My water parameters are and have been in perfect or near perfect range for over a year. I only have a couple of Damsels, Chromis, O. Clown, Sally Lightfoot, snails, smaller hermits and corals in my tank. My biggest worry is that I am only prolonging a horrible life of immobility! Is it possible that he will regenerate his 3 lost legs? <Please see above.> Or have I literally made him a "sitting duck"? Any thoughts would be greatly appreciated!! <I hope this helps, Brandon.>

Marine crab reef safe? 3/6/07 This guy must have come in as a hitchhiker a while back. I just noticed him today, and as of yet I haven't had any fish come up missing. I do have one millepora that has shown some recent tissue loss, but I{ do not think it is him. Anyhow I know hairy generally means bad, but I thought I would check. He is fairly large, I would say at least 3/4" across possibly an inch. Thanks <Mmm, not "reef safe" on much of a sliding scale... I would remove. Bob Fenner>

Re: Broken heater & resulting contamination (conclusion & Crust. ID) 2/27/07 <Hi Dave!> Well this should be the last post on this subject. <Will miss...> Everything is back to normal, short of the large Sarcophyton still that has not opened its filter parts of the polyps yet, we have seen one or two open but not the whole mass yet. <Give it time. You will notice that they occasionally go through bouts of looking lees-than-great. I don't worry unless they bleach or start to deteriorate.> It seems to bring in its polyps in the evening and stretching out like a hand then closing the fingers together again. I see it do this for awhile then it opens its polyps up again always seeming a bit bigger each time afterward. Is this how they grow? <I'm sure I don't have a grasp yet of the behaviour of Sarcophyton, but I know when to worry. Not yet.> Totally different subject: Last weekend we had a fish jump from the tank (missing cover replaced). <Dang.> When I went to feed in the morning I noticed the trigger didn't come out to eat and I searched and searched the tank (before finding the blue throat on the ground dried up) PICTURE THIS :)... So we are missing the 5" blue throat trigger, in my wife an I's <"I's"? ...you mean my? ;) > search we see this crab come out of a hole in the live rock. Never seen him before, and this live rock has been in several tanks in the house for at least three years. My wife screams OH MY GOD THAT thing ate our trigger !! <Mmm... not likely, though I would consider the *possibility* that the crab may have startled the trigger into jumping in the middle of the night by touching or even pinching him.> Thank god I found the trigger and this cool lil guy isn't to blame. LOL. He has been in a few tanks with many varieties of animals over the last few years and hasn't apparently caused trouble or even showed himself till now. <Would keep my eyes peeled for any aggression on his part. There are precious few crabs that AREN'T opportunistic omnivores. They will eat whatever can't get away from them, and smells yummy.> Can you ID it from this pic? <Sadly, I cannot. I will run it through BobF for you...><<I can't make it out either... are the tips of those claws dark? See WWM re Crab ID... this is very likely a predaceous species... and though small, you will have to make the call to isolate, or remove... BobF>> He lives waaay back in that hole behind him and only came out as far as that. Notice the skewer and frozen food cube for scale. He wasn't bold enough to come all the way to the cube. Thanks in advance, Dave <Welcome, and good -GrahamT>

Acro Crab? Reef Safe? Yep! 2/22/07 HI crew!!, <Hi there! Mich here.> Good evening, last week I introduced this Acropora into my system and found this little guy as a hitchhiker. As far as I have read, asked around and researched, it is an Acro crab and would be safe to leave it there, but wanted to double check with the experts here in WWM. <It is an Acro crab and is safe to leave. Enjoy your lucky addition!> Thanks in advance. <You're welcome! -Mich>
Re: Acro Crab? Reef Safe? Yep! 2/22/07 Thanks for the fast response Mich, so he stays where he is. Cheers! <Welcome! Keep him there! Regards, -Mich> Alfonso Garza

Problem with <true? or hermit, really> Crabs and Overstocking -- 2/20/07 Help! <Hi Janet, Brenda here tonight> I have been reading through your FAQ's and reading elsewhere and I am not finding the answers to my question. Since November 2006 I have had a 24 gallon Aqua Pod. All my parameters are within the required limits. I do a weekly 4 gallon water change to keep my nitrates down. I have 4 fish (yellow-tail damsel, 1 clarkii clownfish, and 2 percula clownfish), there are snails and crabs, mushrooms, an anemone (the clarkii loves it there), a sea urchin, a blue star fish, frogspawn coral, feather duster, star polyp, Caulastrea, Galaxea coral, yellow pagoda, Zoanthid, and 2 cleaner shrimps. <Oh my! You're way over stocked. You will also see aggression between the percula and clarkii clownfish as they mature. You shouldn't mix corals and anemones, especially a nano tank. The Galaxea has sweeper tentacles that can reach up to 12 inches, the frogspawn also has long tentacles and the Caulastrea up to 2 inch tentacles. These tentacles will sting all your corals and your invertebrates.> I had (and these have not survived) a electric flame scallop, black sun coral, pearl bubble coral, brain coral, and Fungia. <I'm not surprised.> I feed them 1X a day ~ I alternate every other day with the following Mysis shrimp, Cyclops Eeze (originally for the black sun coral), and prime reef flake food. About a month ago, I took out 10 crabs (I had 20) because they seem to be eating other things in the tank besides the garbage. <It is recommended to have 1 crab or less for every 10 gallons. I don't recommend crabs with anemones.> Now they seem to be eating snails <This is common they can also eat small fish, corals, and nip at anemones.> and they look they are eating each other, too. <Have not heard of this, could be the sweeper tentacles.> It, also, looks they have multiplied. What do I do? <Decide what sort of tank you want to keep, anemone or coral. If you choose coral, select those that are not as aggressive. Please research compatibility and care before your purchase.> Janet <Brenda>

Camposcia retusa... decorator crab, comp. 2/16/07 Hi Crew <Angel> I have a question regarding the above. I have bought one, I suppose it was a bit of an impulse buy as I wasn't planning on getting one, <Mmm, you're learning...> I'd never heard of one, but I saw it and was fascinated. The shop didn't give me the Latin name but from pictures I have seen on the internet it is definitely this one. It is approximately 10 cm in diameter from tip of leg to tip of leg. <Yikes... Giganto!> So he is fairly large compared to my other shrimp and hermits. So basically I have a tank set up with fish, shrimp (dancing) and hermits (red ones) waiting for my new and improved 700 L new Christmas present tank to cycle. <Wow! Send your Santa my way!> It is a reef set up in that I have live rock in it, 2 types of algae plants, under tank sump, skimmer (thinking of getting an ozonizer to make the water crystal, but that is another question for the future may be). Any way as I have told Bob F in a past email, my LFS only gets small stocks of marine life and quarantines them for about 6 weeks before selling them and I am very good friends with him and the manager and know that all their stock is disease and parasite free. <Mmm, just my usual cautionary note here re... Most all stores, wholesalers even... can't actually promise such... there is just too much going on... mixed nets, containers, staff... to warrant that contamination hasn't occurred, that new livestock coming/going haven't passed things on...> So I took the crab home and very excitedly put it (Kev) straight into the new tank (acclimatizing obviously). Kev is doing really well, but now that I have seen him trundling around and realized how big he is, although small claws, <...> I am worried about what damage he may do to my fish and hermits when I put them in. My LFS friend said watch with small fish and shrimp, but now I am worried what would be classed as small relative to his size and eating habits. <Ah, yes> My smallest fish at the minute is a young clown who is approximately 5 cm. So at the moment I am holding back on transferring my buddies into the new tank. <You are wise here> I know that in the aquarium world you cannot be certain of anything, but I thought you probably know more about their track record for compatibility than most. On a positive note though the Caulerpa sp. I bought had some hitchhiker xenia on it and so I have attached this to the rock and he hasn't demolished it and only took a little, so maybe Kev is the caring type. <Or not caring for Pulsing Soft Corals... as the present "menu item"> Have had no replies on the chat forums so its over to you! Thanks in advance Angela (WWM fan). Please let Bob know that his book CMA is brill!! <Much good help with this tome. I would definitely keep your eye on Kev... and a spot in a refugium to move it/him too not if, but when he becomes too much of a tankmate sampler. Bob Fenner>
Re: Camposcia retusa comp. 02/17/07
Hi Bob <Am everting my lips in my best... well... semi-okay impersonation of MickJ... "Angie..."> Thanks for the swift reply. <Welcome> Would you say he is probably too big for the rest of my fish and crabs who are in shells of about 4 cm? Give it to me straight, don't spare my feelings! My largest fishes are: 12 cm blue Cheeked goby 12 cm long Midas blenny 8 cm long Regal Tang I know that I can return him, sad though I would be. But I don't want to be unfair to my other fish friends. <Mmm... if it t'were me, I would return this Decorator... Too likely to be heartbreaks down the line> What do you mean by "Much good help with this one tome." <Oh, the publisher, James Lawrence is a pet-fish and publishing genius... a delight to work with him and the Microcosm crew> Angela in a dilemma. <BobF, in a heat to get out and work on the garden walk/run the dogs...>
Re: Camposcia retusa comp. 02/17/07
Thanks for that, he will be going back to the shop tomorrow, but he will be in good hands. <Ah, good> From Angela (named after Carly Simons "Angie baby"). Night time here so off to bed. Good night from rainy Manchester.. <Sleep tight... from nice/sunny (today) southern California. BobF>

Emerald crab and cleaner shrimp - 09/01/06 Hello! <Hi Christy, MacL here today.> Thank you for all of your help from the past, present and future! <You are so kind and we all appreciate it.> Three days ago I added an Emerald Crab to my 25 Gallon saltwater tank, 1.022 spg, ammonia 0, nitrite 0. I bought him to control my Bubble Algae. My current residents are a Scarlett Cleaner Shrimp, 2 Blue-Green Chromis, 9 Purple Mushrooms, 2 Red Leg Hermit Crabs, 8 Turbo Snails. Before I purchased the Emerald Crab, I researched and came to the conclusion that large Emerald Crabs could possibly pose a threat to small fish or crustaceans if it was hungry, but most likely a small Emerald Crab would do no damage to the other residents of my tank. <Unfortunately Christy, small ones grow to large ones and to be honest I have seen them cause problems at all sizes.> I haven't seen any sign of aggression between the shrimp and crab. My shrimp molted last night, and I didn't notice his antennas being any different earlier today, I'm not sure if I just hadn't noticed or not, but now tonight.. I've noticed that all of his antennas are considerably shorter than before, except for one which is the same length. <It is definitely possible for something to have occurred during the molt which caused the antenna length to change.> I'm having a difficult time believing that my less than one inch Emerald Crab could have done that. I also can't find one of my Chromis anywhere! I'm now worried that I've got a little green goblin in my tank! My question is could anything have happened to my Shrimp's antennas other than the crab getting hold of him? While molting, could he have lost his antenna length? <My philosophy on this is pretty simple, if things were good before I add some creature then I start having problems after I add them, then I usually take the new creature out.> On a different note.. I have a question about my shrimp's molting regularity. He molts almost every week the morning after a water change. Is it bad to molt so regularly? <In my experience he's molting way too frequently. Are you adding supplements to the water like iodine? That can cause them to molt more frequently. There is a great section on molting in general in shrimp on site, I'd encourage you to take a look at it. MacL>

Crabs in my house 6/27/06 I live in Hampton, VA near a marsh, and we have been having a lot of rain lately. Last week and today there were a lot of crabs in my garage. Is there any way to keep them out of the house? Judy <A row of small melted butter dishes? Actually, installing a flexible guard under the garage doors setting edge is what I would do. See Lowe's, Home Depot... re. Bob Fenner>
Re: Crabs in my house 6/27/06
Thanks for the tip. Actually, I had thought of putting down some Old Bay and hot sauce! <Heeeee! Tasty! BobF, with a bib on>

The tiniest crab?? ever inside a candy cane coral 4/6/06 I just bought a white/extra gum green candy cane coral and just noticed a small hole in the tissue and what appears to be a very tiny crab in it (approx. 3mm) is this uncommon and a reason for concern? I am a wee bit worried- how will i remove the crab if needed? thank you, Russell Thomas <Common (though not often observed) and not a problem... though semi-parasitic in nature, these two organisms live together in the wild. Bob Fenner>

White spotted crabs in trouble... just natural predatory beh. - 03/26/2006 Hello and thank you so much for what you are doing! the life of my crab is in your hands. <Actually yours... my keyboard is all I can touch here> I have a 55 sw tank that is only 2 weeks old. We got our 2 big , white spotted crabs along with 5 hardy fish(1 of them is in quarantine now) <This tank is too new...> They have been very happy at fist, crawling and exploring our tank happily, but not spending any time together. With time though, Hulk (the bigger sized crab) started to attack Harold (a bit smaller guy) periodically. If we didn't feed him as often as he wanted he would attack him as if to say: if you guys don't feed me now I am going to eat Harold. <Will... not William, just will> I interfere when he attacks, pulling him off the poor guy. Now, even after we added shells, Hulk was still a bully, and Harold is now a recluse, refusing to eat, and spending his time motionlessly perched on the very top of our LR mountain. <Some symbology now!> And he used to climb the funniest places, like our filter tube, and be very active. <And trying to escape...> Now I checked our water and it is ammonia and nitrite wise safe. However, our heater seems to be broken and the temperature has soared to 81. Could this be the problem? <Not likely> I am replacing the heater today and have it disconnected for now. Unfortunately, Hulk has also attacked our only snail and she is motionless, too... But it's breaking my heart that Harold is not even eating and probably not going to molt, since he is nowhere near the sand but instead, climbed the highest point in our tank as if to beg: get me outta here! Please, any advice, tip, suggestion, anything at all to save the poor guy? Angel. <... another tank, or trade in the aggressor. Bob Fenner>
Re: White spotted crabs in trouble -- MURDER IN THE TANK!!! 4/6/06
As an update...the smaller guy has almost killed the bigger guy today. Ripped him in half, his guts are outside, <Ah... a goner> chopped off his 3 legs, 4th fell off. We put him in separately, we don't know if the injured crab will survive. <Not likely> I don't have the heart to just pull him out so he is on his own, with his favorite shell, slowly dying... Is there anything I can do, any medicine to speed up healing, what do you recommend to do at this point??? We are so sad. <Mmm, not to be... inevitable... I'd monitor ammonia, nitrite... likely will be "totally" consumed... and soon... if not already. Bob Fenner>

Mystery Crab 3/22/06 Hi, <Good Evening> First, thanks for all the great info you provide. <No problem> I've been reading through the frequently asked questions for years now and find them very valuable. I finally have a question of my own though. I just discovered this crab in my tank and miraculously isolated from the tank and have him in a bucket. I am wondering if there is anyone there that may be able to identify this type of crab and determine whether it is harmful or not. <It's really hard to narrow down to species, maybe someone else can interject here. However I wouldn't leave him in your tank. Inevitably many species will pick at corals or other inverts at some time or another. Do you perhaps have a refugium to move him to?> I appreciate any help you can give me. <Hope that helped a bit. You can also read more here: http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabs.htm> I hope I haven't left any valuable information out, but the pictures will tell more than I can probably. Thanks for all the help you've given me in the past in the FAQ's. -Brad <Have a great one, Jen S.>

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