Anyone had a bad experience with so-called symbiotic crabs?

[texman]

I have purchased many wild acroporas and some of them have come with commensal organimsms (mostly crabs) I have now had at least three seperate acros come with fuzzy little crabs that end up causing significant damage to the corals. The colourful little crabs do no seem to harm the corals, however the brown fuzzy ones do seem to occasionally eat the polyps or at least disturb the branch of coral enough to cause the polps to retract, with the branch eventually dying. I have had to remove the coral to a seperate container and pick out the crab with tweezers. After putting the coral back into the tank without the crab, the coral seems to recover. Anyone else had this experience?

 

[Mouse]

Unfortuanately, yes. But in my expirience keeping well shaven usually stops the little buggers from getting a grip, but a GP should be able to sort you with ............. OH, you mean THOSE crabs

 

[Anonymous]

hi.
Almost all the commensal crabs that I had seem are all hairless, either ivory-white or light brown, with a black slash across the front (eyes). They never harm the coral. I don't have any experience with hairy "commensal" crab, but I do have a few that live in rock and came with my live rocks... The hairy ones like to cut up my Xenia and spread them everywhere

 

[2poor2reef]

I have never had a bad experience with them but my warty frogfish has.

He is very small at less than two inches and within thirty minutes after acclimating him he had chased up a commensural crab that had vacated a stylophora I recently lost. Well, when the angler started to lure the crab caught hold of it's lure and a terrific wrestling match ensued, with the frogfish trying to down the crab while the crab was still holding on to the esca.

The crab won that battle and I've never seen the angler fish for crab again.

 

[Green Mariner]

Just to clear a few things up, hairy crabs are not commensural, they are preditors and will eat your sps. Most if not all commensural crabs for sps are smooth shelled, when I find a hairy crab in one of my sps I promptly remove it and feed it to my mantis shrimp. As seven ephors mentioned they usually have a black band across their face, kinda looks like a mask, there are other types of commensural crabs but these are the most common. IMHO, in general hairy crabs should never be placed in a tank, if you miss one when adding livestock remove it as soon as you notice it in your tank!

HTH

 

[slojmn1]

Just to be the devils advocate. I have a hairy "commensural" crab I have been keeping a very close eye on for 3 motnhs now. No harm to the coral head he sits in. There is also a white smooth bandit commensural crab(that is what I call it due to the black mask thingy) in the same coral head. They seem to get along fine and no damage has been done. Neither crab has vacated or moved to another sps...yet...

I guess we shall see in time

 

[texman]

Thanks Green Mariner. What you said is what I have experienced. None of the books I have, have mentioned that the hairy crabs are bad and so I did not remove them initially. From now on, I will need to inspect my SPS corals a little closer. Unfortunately, it is sometimes very difficult to spot the little buggers in the bigger, tightly branched acros.