I saw this one coming for the past couple days. Since I got more plants to absorb light and ferts, algae growth has been on the downslide. I've been supplementing their diet with boiled lettuce, which the Otos absolutely throw down. The lettuce is always gone in the morning, and 3 Otos have fat bellies. This one didnt, and I wasn't sure what the issue was. He wasn't eating the lettuce. I saw that he was having trouble swimming, so I netted him in the event that he died in a place that I couldn't see and I would have to tear the tank apart to find him. Only took a couple hours.