I came home today to find my crown tail lying on the bottom of the tank. I watched for a minute or so, and saw no movement. But as soon as I reached for the net, needing to move the food, he swam to the surface. He's eating and swimming around now, and there's no visible illness. I just have no idea why he would be lying down? . I've had him for about 5 months, and have had no issue with him.