I have several different crabs in my tank that came with the live rock. They are brown, hairy, and stare at my corals with drool hanging from their mouths.
What are they?
There are many, many crabs that inhabit live rock and are often a real frustrating problem for those that own them. Identifying them is even more problematic due to the sheer numbers of species of crabs found on the reef. There are many species which would cause damage in our tanks, and many more that aren't even described yet. If one were to guess on the species, Family Xanthidae and Family Majidae would probably be the strongest possibilities due to their commoness. It is probably a good idea to remove (if possible) any unidentified crabs before the can become a nuisance. However, think carefully before you decide on a course of action. Diversity is something most desired in reef aquaria, and it would be better leave the crab until there is evidence that it is doing damage. If the crab has been in your tank for a long time and you have no mysteriously damaged corals/missing fish, chances are that the crab is harmless. Innocent until proven guilty....
