I received a free frag from the shop I purchase my corals and it was a slice of purple-rim fungia. I have no idea how to take care off it since it does not seem to have a mouth or anything. It's just a little slice of greenish tissue with ridges and a purple edge. I see no tentacles or anything and at night it swells up but that's about it. I have it at the bottom of my sps tank and I am not sure I can keep this thing, any ideas>?