What Do Fish Eat & What is Fish Food Made of?

By PetMD Editorial on Aug. 20, 2009

If you’ve got a pet fish, you might think feeding him the fish flakes from the local pet store is enough. While it will get your fish through the day, think about this: How would you like to be fed porridge for all your meals, every day, for your entire life? Kinda boring, right?

Variety is definitely the spice of life, but how do you round out your fish’s diet the right way? Of course, you need to do your research for your particular type of fish. But we have a few pointers to help you understand what fish can eat.

Meat Eaters vs. Vegetarians

Like people, some fish eat meat, others don’t. But this isn’t a lifestyle choice. Fish are either omnivores, carnivores, or herbivores. So make sure you know what your fish is, and feed it accordingly.

Never, ever feed your carnivorous fish a diet only consisting of beef. Some people do, but it’s not recommended because fish have a hard time digesting beef. Give the steak to the cat instead, in the hopes she won’t try and eat the fish when you’re not looking. And your fish? Give it little treats such as flies and worms, all of which can be bought at your local pet store.

Low Fat

Nobody wants to see an obese fish lazing about on a plastic castle in the fish tank. It’s just not right! To avoid this, be careful not to over-feed or give your fish treats with high fat content. Excessive fat can damage the liver and even eventually kill them, not to mention give them a complex. Instead, buy only the flakes of the highest quality that list their fat content on the side, along with the rest of the ingredients.

Staple Diet

Which brings us to the backbone of a fish's diet: high quality flaked fish food. What is this fish food made of that makes it a backbone? It depends on the type of food you buy, but most flaked foods are made up of a combination of fish meal, squid meal, shrimp meal, earthworms, spirulina, and vitamins and minerals. This provides your fish with all the nutrients he needs but can’t get in captivity.

Beyond Flakes

What else can fish eat beyond the flakes? There are many different options from frozen to live food. These are all made especially for your fishy friends and are also species-specific. In fact, these foods are close to what they’d chow down on in the rivers and seas.

Of course, remember to defrost frozen food -- you wouldn’t like a still-frozen dinner, would you? Unless it was ice cream, of course …

Here’s a quick description of the options available.

  • Dry food. It comes in flakes, pellets, and sticks. You can store these for a long while, but buy them in small portions (and only when needed) to keep vitamin and mineral quality high. Flakes and pellets are often low in fiber and can cause constipation, which in turn can cause swim bladder disorders and bloating in fish, so make sure the dry food you choose has a high fiber content or supplement with vegetables.
  • Freeze dried. Blood worms, krill, and other crawly things are all great treats for carnivorous fish.
  • Frozen. Just cut off what you need, defrost, then feed. Frozen fish food is high quality, with simple ingredients.
  • Fresh. Some fish will eat a small bit of pea, zucchini, or shrimp. Your fish's type will determine what is healthiest fresh food for it. We recommend partially cooking veggies, then letting them cool to room temperature before giving your fish a small morsel. You can also chop up shrimp, they're absolutely scrumptious (for you and the fish).
  • Live food. You might feel a bit squeamish, but it’s sometimes part of life, and there are some fish that will only eat live food. If you go this route, avoid purchasing live food of substandard quality, and ask the experts at your local aquarium for suggestions.

Now that you are knowledgeable in the highest quality foods available, you can be assured your fish is eating healthy.

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