[reeferious]

as anthony suggested it depends. i've had all three grouped together as frags since from nanoreef setup date although they're now more like weaving forest of tentacles that frequently brush against one another with no ill effects. i believe if they've been maintained closely together when they were quite small and allow to grow and mature together these corals somehow become tolerant of each other's physical and chemical presence and would refrain from stinging those around them, you know like a cat who adopted a little mouse for a best friend simply because they were together since day one.