As a general rule, adult goldfish should be fed a small pinch of food two to three times daily. The portion should be about the size of the fish’s eye. Avoid overfeeding, which can cause water quality problems and health issues.
Factors to consider include fish size, water temperature, the number of fish, and the type of food. Goldfish have higher metabolisms in warm water and slower metabolisms in cool water. Observe your fish’s appetite and behavior, and adjust portions as needed to keep them healthy.