Hi everyone. We have a male Betta fish that lives alone in a (unfiltered) 10 gallon tank. The tank gets regular water changes. He's always been a "sluggish" fish, never moving around too much. But over the last week he has just been floating on his side at the top of the tank. We blamed the water for being too cool and purchased a new heater. The water now stays around 78 F. He has also stopped eating. When we open the tank, he'll get startled and try to swim away, but he'll just float back up. We got him about 6 1/2 months ago. I don't know if it's a swim bladder issue, or some other disease. Ammonia levels seem fine (use API test kit). Everything else is normal. Somebody suggested aquarium salt for goldfish and tropical fish, but I don't know if it will really help. Any thoughts or advice would be very much appreciated!!