Those symptoms could be due to a variety of things... But the first thing that popped into my head (I could be wrong as this is just an educated guess) but nitrate poisoning. The symptoms do match what you've mentioned... Have you noticed any sort of bulge or "growth-like" thing on him?Fu's getting worse. He can barly flap his flippers and hes just lying on the floor. Hes breathing very quickly, is this normal. He cant falp his flippers as much.
Thanks! My bettas also called samurai and i call my cherry shrimp the scavenger ninjas.