I have two bettas living in a five gallon tank with a heater and a filter(they're separated, don't worry) One's a regular betta(Zeus) and the other is a much smaller crowntail(Plato). I used to feed them the same amount but Plato would get bloated all the time while Zeus is just fine. Luckily I figured that out and feed him lots less.
Anyway last week I fed them and Zeus got all bloated, which never happens. Plato was fine. I had slacked off on doing a 25% water change the week before and the water was kind of gross so I stuck them both in jars and cleaned the whole tank. When I put them back I stuck them in opposite sides to see if they would play with the decorations(I have a human skull that Zeus loves swimming in and a crocodile skull that Plato pretty much ignores) and Zeus loved it, he was swimming around and exploring(apparently Plato is just boring.)
The next day Zeus was bloated(I fed them in their little jars during the water change) and I thought maybe he was just stressed so I switched them back, at the very least so Zeus could swim in the skull and be fully underwater. He seemed fine the next day so I didn't think anything of it.
I fed them again Sunday and Zeus got all bloated again but once again was fine the next day. I caught him attacking the rocks looking for food but I figured it would be best to wait a bit. Yesterday he wasn't really bloated but wouldn't swim down. He'd dive down occasionally but he'd be stuck at the top, always being dragged back up.
So I came home today from work to feed them and do a water change and Plato is all fine, doing his little fish thing, but zeus was SUPER bloated. On his side, freaking out occasionally and diving down. I thought I saw his belly hugely bloated so I ran down and got a jar ready and then when I moved him his stomach wasn't bloated at all. But he's on his side and floating like he's bloated, only I can't figure out why because I haven't fed him and his stomach is normal sized. He's breathing kind of heavily and luckily the jar I have him in(it's secretly a brandy glass) is curved so he can kind of be straight up and down but the top of him is sticking out of the water and I can't imagine that being very healthy for him, eh?
And silly little Plato is up there acting all smug I bet.
And advice would be welcome! His fins are clamped down and he looks a little paler than normal, he's usually a super vibrant dark blue with a black head and hints of red and his red looks kind of grey but the blue still looks fine, maybe a little paler.