[dugg]

As i'm sure you have already been told, sun corals are almost impossible to keep alive in an aquarium. He probably isn't getting enough food. You have to feed him 2 or 3 times a day with mysys or brine, using a cup oof some kind to hold the food over him while he eats. They also don't like light, and thier natural position is hanging upside down under a ledge. The problem there is that in an aquarium, it is impossible to get food to them when upside down and in a dark place. They are also very picky about the water conditions. If you feed them like they need fed, unless you have a very large tank, you are going to have a hard time keeping the water clean enough for him.