What you feed your fish — and how much you feed them — is an important part of the environment you're providing. 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 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, starting with whether the species are meat-eaters or 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, 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 tank will help reduce the risk of swim bladder disorders and bloating.
- Frozen Food: Some fish will enjoy frozen food, such as shrimp, bloodworms, plankton, prawn, krill, or mussels. Avoid feeding beef to a carnivorous fish, as it's hard for them to digest. Pet stores often also sell frozen vegetables and spirulina that are meant for fish tanks.
- Live Food: Options include live shrimp, feeder fish (for larger carnivorous fish), and worms.
- Greens: If your fish are the type to munch on aquarium plants, give them greens instead. Options include lettuce, cucumber, zucchini, and spinach. Clip the greens to the side of the tank or fasten it in place near the substrate, but remove or replace the uneaten vegetables within 24 hours.
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 — not only the waste left when the fish do not eat all the food but also the waste being excreted from the fish because they're eating more than necessary. If you find that nitrate levels are going up and the tank seems polluted, you're probably overfeeding the fish.
Because they are cold-blooded, fish don't need as much food to maintain their body temperature. They really only need to 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. Follow the rule of thumb that says you should feed a fish only what they will eat in 5 minutes or less.
There's one exception: Herbivores typically don't have large stomach to hold a lot of food. They can be fed more frequently than carnivores or given live greens that they can snack on throughout the day.
Don't take the size of the tank 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 so everyone can get to it easily.