Mines not killed anything in my tank. The only thing he did attack was a new chalice coral which was already stressed and had tissue necrosis already which i didnt realise at the store. Corals i have/had being blastos, montis, stylos, duncans, gonis, euphyllia,psammocora and various softies.
However minewill pick at corals randomly and may cause reduce polyp extension to certain corals, mainly just the montis as such, but they dont seem to care and continue to grow. Just keep the butterfly well fed and try to introduce after all coral has been added, so nothing is entering his environment new as such.