If you find that the rubber band does not work, here is an almost guaranteed way to get a recalcitrant softie to attach. Use a small tupperware type container that is as deep as it is around. Put the stalk of the Toadstool in that, and surround it with rubble. Put the whole lot on the bottom in a low flow area. The coral will attach to a piece of the rubble in a short time. I attached a couple of really troublesome Colt frags that way.
