Help Please. What is wrong with him?

[Sharon22]

He is a dwarf emerald rasbora. I bought him from my LFS on 2/22. Only had one loss and while I don’t see them much because they are very shy they seemed to be doing well. Colored up and would come out if I left the living room. They’re in a 29 gallon co2 injected planted tank. Water parameters are 0 ammonia, 0 nitrite, 20 nitrate, 7.5 pH, temp of 76.7 F. He looks like his tummy is sank in. He still tries to swim and can do like large jumps but mostly just sits there with labored breathing. I moved him to a holding tank with stress coat and prime and an air stone.   I also fed him some flake food with tongs but he didn’t eat but maybe a bite or two. Also I was gone for two days and my lights and co2 are all automatic so they just fasted from Friday at 8:30am to Sunday and 8:30am. I came back and my tank is COVERED in hydra. It’s on every surface. Since he’s so little (like 1/2”) could the hydra have hurt him?

[Colu]

With the sunken belly   it looks like wasting disease  I would treat all the fish with levamisole active ingredient in expel p once a week for 4 weeks @Sharon22