I gave up on that idea a while ago. Originally, we were very careful as to how we placed colonies, constantly keeping up on fragging to prevent them from growing on the main structure of the rock work to make fragging easy. After things were balanced ever so carefully, we introduced some fish that put things out of balance, and flipped them over. Now, we just glue things to larger rocks, and then when fragging comes, we'll pull off some frags right in the tank.