I have never had one, but from what I understand about them, they are dangerous to mobile and sessile inverts. I believe that they are carnivorous and may eat your shrimp, soft coral, and cleaner crew species. I think I saw a presentation on INHD, or maybe it was Discovery:notsure: , that showed a large army of those things just wiping out everything in their path on a wild reef. The aftermath was unbelievable. Maybe someone else who has had one, or tried to keep one in a reef could hop in here and confirm.