As you said, most of them eat unclean food (hungry), which leads to gastroenteritis (no stool) and the swim bladder is disordered (floating). Treat it quickly, or it's hopeless. Here is how to treat it. First lower the water level, don't feed, raise the temperature twice and have a rest. 1. First aid measures: When the swim bladder is seriously out of balance, soak it in 2% crude salt water 10 minute twice a day. 2. Feed anti-inflammatory drugs such as allicin, Sanhuang powder and compound berberine to treat enteritis. 3. During the treatment, change the feed, reduce the content of protein and oil in the feed, and choose fresh and digestible feed instead of oxidized and deteriorated inferior feed. 4, a change of water can't be too much, more can't change water more than 30%.