I have a 10 gallon tank. With 3 glofish, 6 tetras, 3 fansytail guppies and my late Betta. I have a good filtration system, a heater to regulate the temperature, and an air pump to keep the water oxygenated. At first he kept to himself in one corner of the tank, later when he discovered he didn't have to stay in one corner he was out and exploring the tank and the other fish. He never bothered the other fish, he was peaceful, the other fish never bothered him seeing as he was the largest in the tank. He never showed any signs of disease, he ate shrimp pellets and flake food and brine shrimp when I fed my fish (I give them lots of variety in their diet), he appeared to be an active, healthy, happy fish. But this morning he was lying at the bottom of the tank stiff as a board. If it helps I also found a ladybug floating in the water, but I don't think that matters as none of the other fish were affected. Got any ideas of what might have happened?