They are supposed to be very hardy however they can take some time to fully acclimate to a new tank we had one at my lfs that didn't eat for 2 weeks then he started eating brine then slowly very small chopped krill. you can keep them easily in a 55G tank because they are not active fish. Just make sure you have alot of hiding spots for him and you keep him with really docile tankmates
I agree with Drewsta for the most part.
However, it should be noted that they will definitely eat shrimp and smaller fish. For this reason, they are not classified as reef safe.