well, all i know is that when i got my zoas, my blue legged crabs sure did like climbing on them and i think eating them, i have a video of it... but then when i moved the rock to where the crabs couldnt get to it, the zoas started comming back, but since i had never seen this thing before, i didnt know if maybe it was what was doing the damage at night time and then the crabs were just cleaning up the little bits that were left over.. sounds like its just the crabs, so when i go to move everything from this tank to my new one, i'll just make sure and not put any of the blue crabs in the tank, i'll put them in the fuge.