I have a small Domino Damselfish that is sick. I had got the fish tank from my sgt who got out the army and had to travel a long distance and didnt want to tank the tank with him. When i got the tank it was so dirty that you couldnt see the fish. That was about 40 days ago. its almost to the point to where it is completely clear.. The fish he gave me are a Domino demsel, Javanese damsel, Blue Damsel, Black damselfish juvenile, maroon clownfish and a dimond goby. All the fish are doing great but the Domino Damsel. It stays at the top of the tank with its head in and out of the water, the fins look like they are damaged badly. The color of the fish is faded. I have treated it once before with Melafix and the fish got a little better but still stayed at the top of they tank..now it seems like its getting worse and that the fish is weak cuz he would just float at the top of the tank like its dead. and im treating the tank with melafix again.. its been a few hours and he is swimming again at the top but still looks really sick.. but all the other fish look really healthy any suggestions on what i could do..