I picked up a colt coral, it couldn't be taken on the rock it was attached to so they LFS guy cut the base. To attach it to a peice of rubble I have I put it in a container with some mesh over the top and the rubble and some sand inside. Problem is is that the coral will stay near the rubble, then it will float up and then land again somewhere else. It will never attach this way, what can I do?