I have had a Betta male for about 4 1/2 months now, and he has always been healthy...a fast swimmer and eater, with vibrant colors. His water temperature is just fine, mid-high 70s, so cold temperature isn't an issue.
Yesterday, however, I noticed he was very slow, and his face was greyish in some parts, instead of the usual black. His colors started to fade somewhat, and he was swimming on his side. It still hasn't gotten better, although he eats normally and tries to swim as best he can. He swims crookedly and on his side.. I have already changed his water.
I read online about bladder disease that can cause fish to swim on their sides, but the page said that it's usually caused by overfeeding. I have not changed his feeding schedule or anything, and he has not been eating more than usual. Does anyone know what his problem could be?? Is it bladder disease, or could it be something else? What can I do about it...and will he get better soon?