The moorish idol might give the new additions some flack at first, but it shouldn't extend beyond that. As far the butterfly being reef safe, I haven't seen this species being kept in a reef tank, but I would imagine your SPS would be ignored, and the more likely targets would be zoas, fleshy SPS, clams and feather dusters. You can usually determine the risk of adding a fish by the way it's mouth is designed, and if I were to bet, I would say this guy would probably pose a problem at some point, for at least some of the stuff in your tank. Beautiful fish though, gotta love them butterflies :fish2: