Reef safe, No. They eat crustations. A 55g, barely. Special care, in a 55g you will need a good filter system cause thet eat alot and get mean so limit and carefully select tankmates and get one from the Western Pacific and not the Indian Ocean.
Not a very good idea for the reef. They eat motile inverts like snails, crabs, and shrimp. Only supposed to keep one per tank also. They are quite aggressive. just my three cents.