I noticed a hole and bump in the coral awhile back, but it was increasing in size. It seemed to have no ill effect on the coral so far... but why take a chance. The one piece had more and more little burrows starting out, but there was one or two burrows going through the base of the coral and going in between branches. I had pulled everything out due to a flat worm issue, and decided to wipe out whatever might be an issue. I had two hairy crabs pretending to be acro crabs... they are now dead as well.