They get to about 4" in length and are relatively passive toward most fish except for other hogfish (and a few wrasses). They eat ANYTHING you feed it .... hence the name hogfish They will eat small shrimps and crabs though and very tiny fish, although there are very few fish I can think of that can fit in its mouth. All in all, it's a very good addition to a reef tank if you don't care for crustaceans.