They hate bright light. They could do o.k. in a 55 if they have a large enough cave to live in. That said, the smallest I kept one in is a 125. He'd come out everyday when I walked in the door from work and greet me then go back into his cave away from the lights.Only while it is smaller if you want it to be happy. They are not big swimmers like a tang but they do get decent sized. In my experiance they are pretty slow growing.
They don't move much, they hate bright lights. They can be difficult to get eating frozen food. Mine ate frozen and almost anything I put in the tank.