So on my sedbed use to be a large colony of zoas on one side of my 40 breeder. For some unknown reason some of them were always irritated for about a month. So I dipped and put back and it helped for a day then again some closed. So I moved the colony up the rockwork and they are now fine. Now I put another colony there and the same thing is happening. Its only in that one spot on the sandbed and it doesnt look like they are being eaten just mostly closed. Maybe bristleworms are making them mad I dont know any takers?