I'm not really sure of what to use, but here's a similar story:
When I first bought Waffle, I had him in a tiny 0.5 gallon split tank but I had the divider out to make it bigger until I got enough money to buy a bigger 10 gallon tank (which I have now). So anyways, I had him in the bathroom changing his water and had only had him for about 24 hours. So anyways, I got the water changed out and had him in his little 0.5 gallon tank and had picked it up to take him back to my room. The worst happened and the tank collapsed in between my hand (it didnt break) and the water, the tank, and Waffle all went flying into about a 4-5ft drop into the floor. Waffle landed in the lid of a toilet bowl brush cleaner (not inside it):
And he stopped moving. So I quickly grabbed the tank and ran some water and conditioned it quickly and took a piece of toilet paper and put him back in it. He then sunk to the bottom, lifeless so I had just KNOWN I had killed him but luckily, he came back to the top for air and just hovered at the bottom of the tank for a few hours. He's normal and happy now. x) Poor guy.
I hope your fish gets better. There's hope!! haha