Oscar with difficulty breathing

Question
I have a 75 gallon tank with one Oscar and a plecostamous in it. The Oscar is about 7 in long. The water pH is normal, no ammonia, nitrite and nitrates are very minimal. I have been doing tons of water changes, but can't seem to get them to zero.

Okay so my fish has had this increasingly large spot on the side by his gill that keeps getting bigger. I have tried  Erythromycin, General Cure, Flagyl, Melafix you name it. He was eating fine and didn't seem to be in any distress, but it keeps getting worse.

Well I found out the other day that my vet takes care of fish also. I made an apt today and brought him in. He put him in a towel and was going to get a skin scrape off him and he wasn't watching him and he fell onto the floor (3-4 feet drop) and then flopped around the whole room on the concrete floor while he was trying to catch him. He was concerned you could tell. The skin scrape showed very little bacteria and he said to keep using Melafix and get more Flagyl.

I got him home and put him immediately in the tank. He has been gasping for air for the last 7 hours and I am just sick over the situation. I have two air stones in there and the filters are producing bubbles. Is there anything else I can do? I appreciate any other suggestions you have, thanks.

Answer
Hi Danielle,
Poor Oscar, what a terrible thing to happen.  He is stressed by what he has gone through.  If you have not already done so, add 15 teaspoons of diluted aquarium salt to your tank.  Aquarium salt helps fish with stress.  He may remain in this state for a day or two.  Oscars are intelligent, and he won't forget this in a hurry.  Poor thing.
Follow what the vet says.  Melafix is a natural medicine, and should help him.  I would wait tell he is back to his old self before medicating him.  Melafix is okay to use right now, but anything else, wait tell his breathing is back to normal.
Hope he comes back to his normal self soon.
Lynda