What Do Fish Eat? A Guide to Carnivorous, Herbivorous, and Omnivorous Diets!

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Feeding your pet fish a correct diet is vital for their health and vitality.

But what do fish eat?

Fish can be meat-eating carnivores, vegetarian herbivores, or omnivores that enjoy both meat and plant matter in their diet. Offering your fish the wrong diet can be disastrous, so you need to research your chosen species carefully to be sure you feed them correctly.

Read our guide to learn more about the kind of fish foods that your pets need to thrive.

What Do Fish Eat?

For your pet fish to remain healthy and thrive, they need a high-quality, balanced diet that contains protein, fats, and carbohydrates, supplemented by essential minerals and vitamins.

Feeding fish in aquarium

Each fish species needs a different diet, depending on whether the fish are carnivores, omnivores, or herbivores.

What Do Carnivorous Fish Eat?

Carnivorous species of fish eat an exclusively meaty protein diet. The meat content of the diet can be live, dead, or a combination of the two.

Carnivorous fish species include the following:

  • Arowanas
  • Killifish
  • Piranhas
  • Pipefish

Some fish species, such as bettas, are not exclusively carnivorous, including some algae and plant matter in their diet.

Carnivores have sharp, needle-like teeth designed for grabbing moving prey and ripping off chunks of meat. These fish usually have large mouths, a short digestive tract, and big stomachs.

Carnivorous fish are typically hunters, pursuing their prey by hunting or by lying in wait for their prey and launching a surprise attack, while others are scavengers, eating dead fish and animals.

Typical Carnivore Diet

A carnivorous fish’s diet contains 45% to 75% protein, along with some fats for insulation and a little carbohydrate for energy. Some carnivorous fish do eat small quantities of plant material or algae, specifically for the carb content.


Best Foods For Carnivorous Fish

There’s a variety of meaty foods that you can feed to carnivorous fish.

However, we don’t recommend feeding mammal meat because it’s usually very fatty. If you decide to feed your carnivorous fish some beefheart, trim off excess fat first, and only feed in moderation.


Insects make a good protein source and are readily available in live, freeze-dried, or frozen form.

Popular meaty foods for carnivorous and omnivorous fish include the following:

  • Blood worms
  • White worms
  • Tubifex worms
  • Micro worms

Unfortunately, live foods often come with hitchhikers in the form of bacteria and parasites, so be very careful to obtain your live foods from a reputable supplier or breed your own. For the same reason, never take live foods from the wild environment.

For that reason, we recommend using frozen food or freeze-dried food for these types of fish rather than live food.


Predatory hunters will often only eat living foods, including feeder fish, such as feeder guppies, minnows, and goldfish. However, other carnivores will accept frozen or cooked fish.

feeder guppy
Image Source: www.instagram.com

Since feeder fish are often kept in poor conditions and are frequently diseased, we recommend keeping them in quarantine for two weeks before feeding them to your carnivorous fish.

Alternative Live Foods

Brine shrimp and daphnia are inexpensive alternatives for these types of fish and can be raised at home.

Supplements And Dried Foods

Carnivorous fish can also eat commercially prepared dry fish food, and you’ll find more information on that in the Omnivore section of this guide.

What Do Herbivorous Fish Eat?

Herbivorous types of fish eat plant matter exclusively. That food is high in fiber, and the herbivore’s digestive tract is very long to cope with that diet.

Herbivorous freshwater fish typically eat a plant-based diet that can include:

  • Plants
  • Algae
  • Fruits
  • Veggies

Herbivorous fish don’t have stomachs. Instead, the fish’s intestinal tract constantly processes the food. So, herbivores are constant grazers with flat teeth that they use to grind the food before swallowing it.

Macro of algae with many little bubbles in aquarium

Herbivores are also essential in the ocean reef environment since they control algae and maintain an ecological balance.

Recommended Foods

Plant Matter and Algae

Wild herbivorous freshwater fish graze on algae and certain plant species, and the same applies to tank-kept fish.

However, you need to support your fish with some extras, such as algae wafers and fish flakes.

Fruits and Vegetables

Fruits and vegetable matter contain all the minerals and vitamins that herbivorous fish need. So, give your fish some blanched veg, including spinach, lettuce, zucchini, and peas, and a few fruits such as apples and pears.

Supplements And Dried Foods

Herbivores fish can also enjoy flake foods, as outlined below.

What Do Omnivorous Fish Eat?

Omnivore fish eat a combination of plant matter, some algae, and meaty protein.

Feeding omnivores is pretty straightforward, as they eat a mixture of everything mentioned above.

Vitamins And Minerals


All fish need vitamins and minerals for growth and healthy development.

Typically, fish need:

  • Vitamin C: for bone development, healing, and digestion
  • Vitamin B6 and B2: for enzyme production
  • Vitamin B1: to break down carbs
  • Manganese, calcium, and phosphorus are essential minerals for all fish

Recommended Foods

Omnivores only need around 40% protein in their diet, so enjoy a mixed diet of some meaty protein with more plant matter.

Commercial Fish Foods

Dry foods come in various formulas to suit various fish species. You can buy different types of food, including flake fish food, granules, pellets, discs, and wafers. Choose pellets and flakes for fish that inhabit the upper area of the water column, like bettas, and sinking wafers for bottom-dwellers, such as catfish.

Look carefully at the ingredients list on the product packaging to see that the food isn’t full of padding. The best quality dried fish foods contain whole meaty protein, including shrimp, fish, and squid meal, together with earthworms and Spirulina.

Omnivorous fish also enjoy frozen types of fish food, especially those that prefer a protein-rich diet.


Some fish don’t fall into one of the above categories.

For example, some fish of the Panaque and Hyposomus genus eat wood! These fish also graze on algae that they scrape from driftwood as part of their diet.

Some marine cleaner fish and inverts eat the microbes, dead skin, and parasites that attack some ocean creatures, while others are cleaner fish, venturing under the gill covers and into the mouths of larger, passing fish.


In this section of our guide, we answer some of the questions most commonly asked about feeding aquarium fish.

Q: How often should I feed my fish?

A: It’s crucial that you don’t overfeed your fish! Overfeeding causes problems such as bloating and constipation for your fish, and uneaten fish food rots on the substrate, polluting the water and placing a higher burden on your filter system.

I feed my fish twice daily, with one day every week when I don’t feed them at all. I give my fish only what they will eat in a few minutes. One day’s fasting allows residual food to clear the fish’s digestive tract before more is added, helping to prevent health issues.

Q: What is a fish’s favorite food?

Assorted different types of food for aquarium fish. Flakes, spirulina, pills, mixture. Navy blue sea background, close up

A: That depends on the fish species and the individual fish! I once had a Ryukin goldfish that loved zucchini while his tank mate wouldn’t touch it. Most fish enjoy special treats outside of their regular diet. It’s up to you to work out what your fishy friend’s favorite snack is!

Q: What do fish eat in the sea?

A: Ocean fish eat small crustaceans, including krill, prawns, shrimp, crabs, barnacles, lobsters, and the like; large mollusks and invertebrates, and larger fishes eat small fish species.

Q: What food can fish not eat?

A: As mentioned below, you should never feed your fish bread. Crackers, cake crumbs, and similar are not good either since they contain additives that could harm your fish and might swell up in the fish’s digestive tract.

Fatty meat is also not good for fish, nor is a dog or cat food. Remember that fish can survive quite happily without food for a day or two, so don’t panic if you’ve run out of your fish’s usual food; they will be fine until you can get to the fish or pet store for supplies!

Q: Can a fish eat bread?

A: Many fish will happily eat bread, and some owners routinely offer it to their fish. However, bread and cake are not good fish food substitutes!

Bread and Crackers

How so?

Bread swells when it’s exposed to water. So, when the fish eats a piece of bread, the bread swells inside the fish’s digestive tract, causing constipation and bloating. Constantly feeding bread to your fish will quickly make your fish sick, and it could even die.

So, don’t feed bread to your fish!

Q: What do fish eat in the wild?

A: In the wild, fish eat small invertebrates, crustaceans, worms, insect larvae, insects, small fish, plant matter, and algae, depending on the fish species. Some large, predatory fish also take frogs as part of their diet.

Q: What do small fish eat?

A: Small fish eat whatever they can fit into their tiny mouths! Many small fish eat algae and plants, as well as tiny insects, microworms, and baby brine shrimp.

Final Thoughts

I hope you enjoyed our guide on what fish eat. If you did, please share the article!

Your fish won’t thrive if you feed them incorrectly! So, when choosing fish for your collection, be sure to research the species carefully so that you know what nutrition they need. Most fish can eat frozen or dry commercially prepared foods, but you can include live foods or even take the DIY route and make your own fish food.

What do you feed your fish? Tell us in the comments box below.

Alison Page has been an avid fish keeper for over 35 years and has owned many different species of freshwater tropical fish including bettas. Currently Alison has two large freshwater tanks. The first tank has two huge fancy goldfish who are almost ten years old and still looking as good as ever. In the other, she has a happy community of tiger barbs, green tiger barbs, corydoras catfish, platys, and mollies.

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