I wouldn't put one in a reef tank; I can't vouch for whether or not they eat corals, but they get huge, some species up to 22". Plus they school, feeding much like mandarins (often and in small amounts). There's a reason they're called goatfish. They'll eat most things: worms, snails, crabs, and other mollusks and crustaceans make up most of their diet in the wild. Or essentially, your clean-up crew.
The bicolor, which I assume is what you're interested in, grows to a foot or so. It'd destroy any frags lying on the rock, probably, and may or may not eat them.