I keep my like corals in the sand on the bottom. I have a biocube, so there is like 22" between the power compacts and the sandbed. I have a moderate amount of flow for my tank, basically gently whooshing the tentacles around (Hydor flo deflector). Mine seems to be doing brilliantly. You can try to target feed the coral. It might like that. Alternatively, you could trade him to someone to see if they can't get him healthy for ya.