Wilson died this morning. I just woke up, and he was on the bottom, on his side, not a breath of movement.
I think it might have been my fault. His water temperature was much too high, because I put a small heater in his tank. It was at 89 when I got home from work (!!!!), and so I decided to take out some tank water, mix in some cold, conditioned water, and pour it back in. Looks like it was too much for the little guy.
Edit: I was wrong. Cause of death is unknown. Apparently he made it through the night. My boyfriend checked on him this morning, and he was swimming happily when he left 5 hours ago.
Edit again: Is it weird that I cried over this, or is that just a result of PMS? My friend was like, "He's only a fish, don't cry!" and I realized that it sounded weird, me crying over a fish that I've owned for two days.