Gold fish have a typical life span of 20-30 years. However, they are actually very difficult fish to keep. Unless you replace the water very, very frequently

Gold fish have a typical life span of 20-30 years. However, they are actually very difficult fish to keep. Unless you replace the water very, very frequently (like every day or so), the recommended amount of water is 10 gallons (~40 liters) per fish! Most people put gold fish in ridiculously inappropriate bowls/tanks and think that they live for only a few months or a year. As someone else pointed out, the reason your fish lived longer when you fed them less is because you were reducing the amount of ammonia (from rotting food, or from fish waste) in the water.