Goldfish sit on the bottom of the tank when they are stressed. Other signs of stress in goldfish are gasping at the top of the tank, not eating, sores on their bodies and swimming frantically around the tank. If goldfish seem stressed, the owner should consult a veterinarian.
Often stress in goldfish is caused by improper conditions in the habitat. Their water may be dirty or the incorrect temperature, or there may be too many fish in one tank. Other possible habitat problems include a chemical imbalance in the water, or the tank may be in a noisy area that disturbs the goldfish.