I don't think detrius is the problem, because there is really good flow in the tank. This rock is a fairly new addition to the tank, the colony looked pretty healthy, though a few polyps were closed - now the colony is just about gone. I'm afraid that whatever has been snacking on these zoas will move onto my favorite ones, so I want to get something in there to eat the critters before that happens. The critters that I'm seeing constantly on these polyps look like typical amphipods, but when I shine a flashlight on them their eyes kind of glow yellow.