Valid concern with rbta! I wish I had put mine on a small island before it grew enormously... had to remove the rock it was on before giving it away!! I love GSP but you have to be careful with that too as it can spread where you don't want it to very quickly!!Great! Maybe I could take a few when getting something else from your tank (was tempted by your rbta while concerned that it will move around my small tank and kill all my corals )