Hello,
So for this anal prolapse issue. I gave the cat fish an epsom salt bath. 1 table spoon in 1 gallon of water for 10-15 minutes. And the problem went away. I just bought unscented epsom salt crystals at the store. I have a 55 gallon tank. I then added the gallon with the epsom salt to the tank then had a water change in a week. Fish is healthy as before.
I hope he stays that way. Usually, there is a hernia and the weak point doesn't heal. The intestine goes back up, but may drop at any point. Keep his food small, and don't overfeed him. No big chunks of stuff!