I have had my beta fish for four years now.
About three weeks ago I noticed he hasn't been actively looking for food when I feed him, and a week from now he hasn't been eaten anything. so I think he probably hasn't eaten anything for almost 3 weeks. He also stopped moving around and he stays in the bottom hidden. The gills movement also seem very slow.
He is in 1 gallon tank, with pebbles and a plastic plant. I usually changed the water every two weeks, but lately I have been changing the water every 3 weeks. I use tap water, use water conditioner and half teaspoon of marine salt. I usually prepare it 24hours before the water change.
I feed him with dry pellets, which usually he accepts really well. I don't have a heater, so the water remains at room temperature which is usually around 72 degrees.
I have to accept that the water wasn't really clean, and yesterday when I was changing the water I noticed that he has kind of a blister (his skin forms like a bubble) at his tail fin, just where the body ends. It seems like an infection, and the bottom part of the body, under the mouth, is turning white-ish.
I treated him with Jungle fungal clear, and it has been in that treatment that for almost 40 hours. I also did read that could be swimming bladder problems and actually his tail seem to be heavier for him. Also he is a little bloated, but I just noticed it today. He is no pooping, but it can be just because he hasn't eaten.
Some times he seems to be resting a little in one side.
I prepared fresh water with fungus clear today and I planning to change the water tomorrow morning or part of it. And also decrease the level of water so he can get air more easily.
I don't know what else to do. I know that he is an old folk but I don't want him to suffer plus he has been with me so long.