They are not 100% reef safe.They are good at eating aptasia and will often take out any colonial or ornamental feather dusters as well. They are a tough fish to get to eat..and often are picky with what they will eat. Most I have seen will take frozen mysis shrimp. When considering buying one..make sure they are eating at the store. They should not be put into new or small systems. All butterflies are delicate,and should be added after the tank is established and somewhat mature.The 8-10 month mark would be safe. They grow to about the size of a dinner plate,so keep that in mind.They should be kept with caution in a reef..and will sometimes nip at open brains and other LPS,and clam mantles.