Commercial goldfish food provides the vitamins, minerals, fats, carbohydrates and proteins goldfish need, but feeding them other foods adds interest and variety to their diets. Goldfish are omnivores, and eat a wide range of plant food and food from animals, including live food. Overfeeding goldfish is bad for their health and the water quality in their aquariums. Feed goldfish different foods in place of their usual diet, and not as an extra treat.
Commercial goldfish food -- available as flakes, pellets and granules -- contain all the nutrients goldfish need, and should form the major part of their diets.
Overfeeding goldfish allows uneaten food to decay and contaminate aquarium water. Goldfish feces is another contaminant. Goldfish don't have a true stomach; food they don't digest passes through their bodies and is excreted.
Feed goldfish two or three time a day, and give them as much food as they can eat in two minutes, or as much as the size of a goldfish eye, per fish. Floating pellets are useful for feeding goldfish because you can scoop uneaten food out of the tank. Soak freeze-dried food before giving it to goldfish to avoid stomach upset.
Don't feed goldfish betta food or other tropical fish food because the nutritional needs of the fish are different.
Goldfish eat vegetables, oranges and live plants. Peas, cucumber, chopped broccoli, spinach and other leafy greens are healthy foods for goldfish. Chopped broccoli can make the aquarium water cloudy, however. Cook vegetables for a minute or two in boiling water, and allow them to cool before feeding them to goldfish. Break oranges into tiny pieces.
Live plants goldfish like to eat include duckweed (Lemna minor), anacharis, azolla and salvinia.
Pet stores supply live and frozen invertebrates as goldfish food; you also can feed them some animal foods humans eat. Goldfish eat fish eggs, bloodworms, mosquito larvae, tubifex worms, daphnia and live and frozen brine shrimp.
Animal foods for humans that goldfish also eat include scrambled eggs, cooked rice and cooked meat, providing all the fat is removed. Place these on the surface of the water, the same as other goldfish foods, but chop meat very finely before serving it to goldfish.
Foods to Avoid
Animal fats, breadcrumbs, uncooked peas and cooked lettuce are bad for goldfish diets. Fats from meat and offal are difficult for goldfish to digest. Feeding breadcrumbs in place of pellets or other commercial foods is harmful as bread doesn't contain the nutrients goldfish require.
Don't feed goldfish uncooked peas, because these can give them digestive problems. Lettuce for goldfish must be raw, as tough strands of cooked lettuce can catch in their throats.