I have a large 50+ colony of zoas that is receding from the middle. I dipped it in Coral Rx last weekend and this weekend as well. The healthy polyps look fine and the rest of the tank is great. The only thing that came off during the first dip was some pods. I may frag it soon to separate the healthy from the unhealthy ones but I wish I knew what the problem was. Would more frequent dips help? Dipping in something else? I'll take all the help I can get!