Research your fish species. People at the store where you purchased your fish should be able to help you pick out a fish food if you cannot find information specific to your species online. Find out whether your fish are herbivores, carnivores, or omnivores, and ideally the exact % of protein the fish species requires in its diet. Some exotic species require special diets, but most fish can be fed basic "fish food" flakes or pellet. However, don't go rushing to the pet store yet.
Find a fish food specific to your fish if possible.
Many aquarium fish are fed with a general purpose fish food, or one intended for a broad category such as "tropical fish." As long as you read this section carefully, your fish may do fine with the right type of general food. However, if you can find a fish food specific to your fish species or group of related species, your fish will most likely be healthier and happier. These should be labeled clearly as "cichlid food," "betta food," etc.
- It's still a good idea to follow the other steps in this section to check a fish food's suitability before purchasing it.
Pick food that floats, sinks, or slowly sinks depending on your fish's mouth shape.
You can ask an aquarium store employee for advice if necessary, but often watching your fish's behavior or mouth shape will be enough to find out what type of food to buy. Bottom feeders such as catfish spend time at the bottom of the tank, with their down-turned or underside mouths searching for food. Mid-feeders have mouths pointing straight ahead and search for food in the middle of the tank. Surface feeders have upturned mouths and cluster to the surface when they are fed. If you are unsure what type your fish is, simply try out a food and see if they successfully find and eat it; some fish may not be restricted to one area.
- Flake food floats, and is only suitable for surface feeders.
- Grain, granule, or pellet food may float, sink slowly, or sink rapidly. Try to find more information on the label before buying.
- Wafer food sinks to the bottom, and is usually too large to be "stolen" by surface feeders.
- Tablet food can be dropped to the bottom of the tank, or, sometimes, stuck to the inside wall of the aquarium to provide food for mid-feeders.
Check the protein content of the fish food.
Use the results of your research to narrow down the type of fish food to buy. Herbivores and omnivores require fish food made mostly from vegetable material, such as spirulina. Depending on species, their fish food should contain anywhere from 5% to 40% protein, so research the species thoroughly to narrow down your options. Carnivores, on the other hand require a diet between 45% and 70% protein, depending on species. Make sure the fish food you buy matches the needs of your fish.
- Bettas are carnivores and surface feeders. Their food should contain at least 45% protein, float, and be small enough to fit in the betta's mouth. Betta food is often sold in the form of tiny pellets.
- Goldfish are omnivores, and require 30% protein as adults, or 45% as young fish. Aquatic plant proteins are easiest for them to digest.They are surface feeders, so flakes are a good choice.
Make sure your food is small enough for your fish to eat. Many fish swallow their food whole, which means they are unable to break apart large flakes or pellets that do not fit inside their mouth. If the food you are giving your fish is going untouched, or if it looks bigger than your fish's mouth, crush it into pieces before feeding or find a smaller type of food.
Look up fish food companies online. Before purchasing a dry fish food, search for the brand name and reviews. Well-respected companies that get good reviews from aquarium hobbyists are more likely to make high-quality fish food.