I don’t know if it’s a male or female but he/she has a bubble forming on its side. Any ideas what could be going on?
Flushing is not a good way to euthanize. It's irresponsible, as you're making the fish suffer and you risk infecting natural water ways.
Mary was suggesting you euthanize the fish, not a vet. There are very cheap and humane ways to do this.