My betta Euphrates has been having, say, issues, lately. He used to eat without a problem, but now whenever he manages to eat something, he seems to choke on it, as in his gills won't close in, and he swims erratically for a minute or two before sinking to the bottom of the tank and breathing heavily. Eventually he spits it out and eats it again wihtout a problem. He does this with any food, bloodworms, tankwater-soaked pelets, everything. Just recently, as in yesterday, he has been listless and not swimming, just laying at the bottom of the tank. It's really starting to get me worried.
1. Euphie used to be active and happy --> Now he's listless and droopy and ignores food.
2. He used to eat without a problem, and in fact he used to be quite the pig --> Now he ignores all food, and if he ever eats anything, his gills don't go back in and he swims erratically then sinks to the bottom of the tank.
His water is changed 90% every week. It's not cycled. It's filtered and heated, with a constant tenperature of around 79-80 degrees. It's planted and is 2.5 gallons.
If someone could please tell me what's wrong that would be great.