I changed my betta's water (I don't have a filter and I know you're all gonna tell me to get one; I know. I'm working on it.) He was fine for several hours after the change but I noticed about twenty or so minutes ago that instead of swimming around like he usually does, he's at the bottom of his bowl, on his side. His breathing is very lethargic and he's only gone up to the top for air twice, after strong persuasion. I tested the water and it's fine. It's exactly the same as the water in the second bowl with another betta, who is acting perfectly normal. I haven't noticed anything different about him at all recently. I keep looking back at him and seeing that he's moved around the bottom of the bowl, but he's still at the really uncomfortable angle, and barely breathing. Does anybody know what's wrong with him? Is there anything I can do to help? I don't want him to die, but if he does, I want to make it as painless as possible.