Provide your goldfish and other pond fish with healthful, live foods. Keep a varied supply of plants so fish can choose what they want to eat. Not only do adult goldfish eat live plants, their young live and feed within plants' roots and foliage. Live plants also provide nutrients and regulate the temperature and toxin content of the water.
Duckweed (Lemna minor) is a perennial water cover that goldfish and koi find irresistible. This quick spreading plant will double in size on a daily basis, if given proper growing conditions. Remember to keep a sufficient amount in a sunny, fish-free area to ensure a constant supply. A sufficient amount is several cups of the plant. Duckweed is hardy in zones 6 to 10.
Azolla (Azolla filiculoides) is a small, free-floating water plant. Goldfish enjoy eating azolla almost as much as they do duckweed. Azolla has fern-frond-shaped leaves, small roots and produces fall-like colours in shades of orange, red, gold, purplish and green. This colouring makes it an unexpected treat to the eye. Azolla is hardy in zones 7 to 11.
Bladderwort (Utricularia inflata) provides a good food-collecting habitat for goldfish fry (young). Bladderwort grows beneath the surface of the water, either by floating or when weighted down. Adult goldfish also eat this plant. Although carnivorous, bladderwort bladders usually catch minute living organisms, not fish. Bladderwort is hardy in zones 2 to 9.
Water lettuce (Pistia stratiotes) is another free-floating aquatic plant attractive to goldfish. They especially enjoy eating the young, tender plants. Water lettuce prefers full sun and is winter hardy to zone 10.
Goldfish will also eat many of the plants humans consume. Tomatoes, green beans, peas, carrots, lettuce, sweet potatoes, squash, squash blossoms, cucumbers, bell peppers, okra and corn are vegetables that goldfish enjoy. The occasional treat of fruits and nonpoisonous flower blossoms is appreciated as well. Quickly blanch these foods to soften them.
Plants to Avoid
Avoid feeding fish plants you know to be poisonous. Deadly nightshade, high amounts of preservatives and added flavours, tomato and potato foliage and large chunks of food can all cause problems for fish. Feed your goldfish plants that it would encounter and consume in the wild.