They grow large and become aggressive. If they don't like the way you arrange the tank, they'll rearrange it. They are strong, and can move quite large rocks and corals. I would train them to eat out of your hand as soon as you can. This is the only way I have found to keep them from biting as they get older. If you keep them fed well, they are very long lived fish. Lots of personality. Really cool fish IMHO.