I had one of these before. Pretty funny because I had it for a long time and would only see it in rare occasion but on my acros. I put him in my sump for a while and i was doing some rearranging of my corals and some how got back in the DT weird. Well, to answer your question I think they eat sps or at least find a week one with damage and start to much on it. I have no proof but thats what I think. Even if its eating decayine acro I think it stress it out to where if the sps had a chance it will not make it because they are not giving it a chance to recover hth.