As I mentioned earlier, goldfish will basically eat anything they can get into their mouth. Which doesn’t mean you should share your morning donut with them. There are plenty of high quality flake foods specifically designed for goldfish as well as sinking and floating pellets. If you choose pellets, try to purchase the sinking kind. When goldfish feed at the surface they tend to gulp air that can lead to swimming problems.
Other choices include live food, particularly brine shrimp. They are available in most pet shops and are sold in half-ounce increments. You can store them in your refrigerator in a plastic container and they’ll live quite happily for two to three days. I use a plastic measuring cup to transfer them from their container to the tank. Brine shrimp are also available in frozen cubes if your family objects to little creatures swimming around in the fridge. One cube is more than enough for a single goldfish. Bloodworms are another frozen food that goldfish love. However, they are quite high in protein so you wouldn’t want to feed these every day.
Goldfish are omnivores, meaning they eat both animal and vegetable matter. One of the things my goldfish loves the most is peas. Besides being nutritious, peas are also high in fiber, which is very beneficial to goldfish. A goldfish doesn’t really have a stomach. Instead it has what is known as an alimentary tract. It’s in everyone’s best interest to make sure this tract is “clog free.” To prepare frozen peas place them in a sieve or colander and run them under hot water for a few minutes. Generally speaking, goldfish prefer their peas without the skins on.