I changed Gareth's water on Saturday and treated it with water conditioner, same routine as normal. I did leave him out of the bowl for longer than I normally do, but not longer than he stays out when I go home (I'm a college student).
After I got him back in, he didn't want to eat anything, but he goes through cycles of wanting to eat a lot and not wanting to eat anything. He's also been sitting near the bottom a lot, but he goes through periods of doing that too.
What really started to worry me was that Gareth is usually a very friendly fish; when I turn his light on in the morning, he always perks up and comes to the front of the bowl then gets ready to eat. He's usually pretty active and curious (?, he likes to come to the front of the bowl whenever I'm around). Now he's starting to act very skittish. When I turn on the light, he hides near the back, and when I try to give him food, he swims away from my hand.
To make it worse, yesterday evening, he started to lean slightly to one side. He sometimes rights himself whenever he swims, but not always.
I don't see anything odd with his appearance, but he may be a little bit bloated. It's hard to tell, but I don't see any poop on the bottom, so I'm guessing that could be his problem (at least that's what I gather it might be from others' problems).
I'm just not sure because I've never had this happen before (I've had him for about 1.5-2 years and had another before him). What does it sound like to you?