Hey guys, need help, catfish not eating.

[Archer33389]

Hi everyone, I have an 8 inch marble sailfin catfish in a 29 gallon tank. I know this is to small but he is alone and I had him in my 125 gallon but he got beat up by the bullseye catfish, so I am trying to treat him for an infection with melafix in this smaller tank and let him grow.I have a piece of pvc pipe in the tank along with fake plants. I have a filter that does 200 gph on the tank. The tank is brand new, I set it up on the spur for him to get him out of harms way. He was eating krill in the 125 but know he just ignores all food I put in. I have tried krill and giant mysis frozen shrimp. Any ideas to try and help him out? It has been roughly 1 week since he last ate and kept something down and his stomach is getting sunken in. I know it may not work but I figure its better than nothing so I have been adding a product called Nite-Out II to try to help get rid of ammonia. Anyone have ideas? thanks