Is there such a thing as a coral eating snail? I just had a shell on a blue tipped acro that I thought died there and it was bleaching out around it....today I see it moved to my green acro colony and its tip were sliming...The thing was really latched on there and looks like a conch like shell....He doesn't have a "flap" but he was retracted all the way in that shell and look empty any ideas?....Jeff