What you feed your fish—and how much you feed them—is an important part of providing a healthy environment for them. There’s much more to offering the proper diet for a fish than just sprinkling a few flakes on top of the water a couple of times a day.
Choosing the Right Food
The fish food section at the pet store can be overwhelming to a novice owner. First, learn more about your fish species, starting with whether the species are meat-eaters (carnivores) or vegetation eaters (herbivores). From there, options to choose from include:
- Dry Food: When you think of fish food, you think of flakes. That's the most common option for feeding a tankful of fish, but dry fish food also comes in granules and pellets, sinking, and floating varieties, as well as options for specific species. Dry fish food can be lower in fiber, but adding vegetable foods to the diet will help reduce the risk of swim bladder disorders and bloating for vegetarian species. Pet stores may also sell sheets of dried spirulina or nori algae, which are great for herbivorous fish to nibble on.
- Frozen Food: Some fish will enjoy frozen food, such as shrimp, bloodworms, plankton, prawn, krill, or mussels. Pet stores often also sell frozen spirulina cubes for feeding herbivores.
- Freeze Dried: Tubifex worms and Mysis shrimp or other foods can be found as freeze-dried cubes. These are very nutritious and great for carnivorous fish.
- Live Food: Options include live brine or ghost shrimp, feeder fish (for larger carnivorous fish), crickets, and worms.
- Greens: If your fish are the type to munch on aquarium plants, such as anacharis, give them greens as well. Options include lettuce, cucumber, zucchini, and spinach. Clip the greens to the side of the tank or fasten them in place near the substrate, but remove or replace the uneaten vegetables within 24 hours. Fish such as plecostomus love to eat fresh greens.
The biology of different fish means they often need different food. Therefore, if you have a variety of fish in your aquarium, use a combination of food—such as floating foods, slow-sinking foods, and rapidly sinking foods—to ensure they're getting the nutrition they need.
How Much to Feed
Fish owners are more likely to overfeed their fish than underfeed them, which increases the amount of waste in the tank. This is not only the waste left when the fish do not eat all the food but also the waste is excreted from the fish because they're eating more than necessary. If you find that ammonia, nitrite, or nitrate levels are going up and the tank seems polluted, you're probably overfeeding the fish.
Adult fish can be fed once a day, around the same time, though you can feed them multiple times a day if you're giving them a smaller amount each feeding. Young fish may need three or four feedings a day. Herbivores typically don't have large stomachs to hold a lot of food, as in nature they would nibble on algae and plants throughout the day. They can be fed more frequently than carnivores, or given live greens that they can snack on throughout the day. Follow the rule of thumb that you should feed the fish only what they will eat in five minutes. If there is food left after that time (except for the fresh greens), you are feeding too much. One exception is for fish that are nocturnal (night time) feeders, where you should put the food in the aquarium in the evening before turning off the lights, and let the fish eat overnight.
Don't take the size of the aquarium as an indication of how much food is needed. Five fish in a large aquarium need the same amount of food as five fish in a smaller aquarium—just spread it out across the aquarium so everyone can get to it easily.
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Clark, Robert. Vanhorn, Beth. Veterinary Assisting Fundamentals and Applications. Cengage Learning, 2012.
Aquarium Water Quality: Nitrogen Cycle. Florida Department of Agriculture and Consumer Services.