thats a hammer coral. the problem with the bubble is its got a 7 inch stem on it. the peice to the left of the hammer is coming out and going in my nano once i buy it... then the hammer will move over there... or possibly the bubble. havent decided yet.
wierd thing is people talk about sweepers hurting other corals... the only coral that has been stung is the green mushroom thats directly behind the hammer. its pretty well nothing now. but i dont care too much. better they sting it then each other