I bought a RTBA a while back and ever since putting it and the rock it came on in the tank, about every other month I have noticed the shed exo skeleton of a crab that I never put in there.(knowingly) I have never seen the actual crab but I have lost random corals while others have been fine. Is there a way to trap him, bait ideas? etc?
You may have to do something like getting a night viewing light so you can see where its coming out from~then you may be able to remove the rock in which it may be hiding in. As far as a trap I'm not so sure. Hopefully someone else will chime in with more experience.
I had one and all's I did was wait for it to come out and then quickly netted it.