What Do Fish Eat? Carnivores, Herbivores, And Omnivores

Feeding your fish correctly is essential for their health and vitality. 

But what do fish eat? 

Basically, pet fish can be omnivores, carnivores, or herbivores. So, what do carnivores eat? Can an omnivore eat meaty foods? And what do herbivores eat?

Read this comprehensive guide to find out more about the kind of foods that your pet fish need to thrive.

What Should You Feed Your Fish?

To remain healthy, fish need a balanced diet that contains protein, fats, and carbohydrates, together with some essential vitamins and minerals.

Man's hand feeding fishes

The composition of each species’ diet is different, depending on whether the fish is an omnivore, carnivore, or herbivore.

First, let’s take a look at the dietary requirements of carnivores.

What Do Carnivores Eat?

Carnivorous fish are the meat-eaters of the fish world. They require a protein-packed diet that consists of lots of live or dead meat. Carnivorous fish species include:

  • Arowanas
  • Piranhas
  • Killifish
  • Pipefish

Some fish are primarily carnivorous, although they will also eat some plant matter and algae. Betta fish are a good example of that.

Carnivorous fish have needle-sharp dentition that enables them to tear off chunks of meat and rip into their prey. These big fish typically have larger mouths, a shorter digestive tract, and a bigger stomach than omnivorous species. 

Most carnivores are hunters, either chasing their prey or hunting by stealth, lying in wait for their prey. Some carnivores are like vultures, scavenging dead fish and animals. Other carnivores eat live insects, insect larvae, crustaceans, invertebrates, mollusks, and live fish. 

Diet Makeup

The carnivore’s diet should contain 45% to 75% protein. Also, some fats are required to provide insulation for the fish’s body, together with a small quantity of carbohydrates for energy. 

Interestingly, many species of carnivorous fish eat small amounts of green stuff, such as plants and algae, purely to provide them with the carbohydrate they need.

In the aquarium, a carnivorous fish needs a variety of frozen and live meaty foods, as well as some algae and plant matter that the fish can obtain from the normal tank environment.

Recommended Foods

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

However, on a note of caution, meat is generally not recommended since it tends to be very fatty. Many owners feed their fish Beefheart, but that should be trimmed carefully to remove excess fat and fed only in moderation.

Insects

Meaty foods derived from insects are readily available in live, freeze-dried, or frozen form, including:

  • Bloodworms
  • Tubifex worms
  • White worms
  • Micro worms

Be wary when feeding live foods, as some can come with a hidden cargo of parasites and bacteria that could harm your fish. I recommend that you rinse any live foods thoroughly before offering them to your fish rather than putting the water in which the food is contained into your tank. For the same reason, never take live food from the environment.

For your peace of mind, you might want to consider raising live foods at home.

Fish
Fish on ice

Carnivores can be fed fish. That can be in the form of frozen, cooked, or live fish. Many carnivorous fish actually relish the chase and can benefit greatly from being offered live fish.

Warning!

Feeder fish are small fish, such as guppies, minnows, and goldfish. However, these fish are bred in huge numbers, often in very poor conditions, and they can easily introduce disease into your tank. Also, feeder fish tend to be low in nutritional value.

If you do decide to use feeder fish, you must put them in quarantine for at least a week before putting them into your main aquarium.

Alternative Live Foods

There are a few other live foods that you can feed your carnivorous fish.

Brine shrimp is an inexpensive food that you can also raise at home and it’s much more affordable than live shrimp.

Daphnia are a staple diet of many tank-kept carnivorous species. Again, you can often buy them cheaply in fish stores or breed your own.

Supplements And Dried Foods
Food for aquarium fish. Photos isolated on white background

Carnivorous fish can also eat dried fish food and food supplements, which are included in the omnivore section later in this guide.

What Do Herbivores Eat?

Herbivorous fish only eat vegetable and plant matter. That food contains lots of fiber, so the herbivore’s digestive system has to be very long to cope with that.

Herbivores typically eat:

  • Algae
  • Plants
  • Fruits
  • Vegetables

Unlike carnivores, herbivorous fish don’t have stomachs. Instead, the fish’s intestine processes the food, and for that reason, these fish are constant grazers. Rather than sharp teeth like carnivores, herbivorous fish have flat teeth that enable them to grind their food before they swallow it.

In the ocean reef environment, herbivores are essential to control algae and maintain the ecological balance of coral reefs. Wild herbivorous fish spend their day grazing on algae, plants, and other vegetable matter. Most herbivorous fish need a very small quantity of meat protein in their diet.

Recommended Foods

Algae And Plants
Siamese algae eater in planted aquarium

In the wild, herbivorous fish can happily graze on algae and live plants, and the same applies in the aquarium. 

However, that’s not usually enough to support these fish and you do need to offer them a few other options, including flake foods formulated for herbivores and algae wafers.

Fruits And Veggies

Fruits and veggies are packed with the vitamins and minerals that herbivores need.

Herbivores appreciate blanched veggies, such as peas, spinach, zucchini, and lettuce. Some fruits can also be included in the diet, such as pears and apples.

Supplements And Dried Foods

Herbivorous fish also eat dried fish food and food supplements, which are covered in the omnivore section below.

What Do Omnivores Eat?

Omnivorous fish eat a mixture of both plant matter and meat.

These fish are probably the easiest fish to look after, as you can feed them a combination of everything already mentioned above.

Vitamins And Minerals

Carnivores, omnivores, and herbivores all need vitamins and minerals to generate optimal growth and promote healthy development.

The vitamins that your fish needs are specifically:

  • Vitamin C: promotes bone development, digestion, and healing
  • Vitamin B6 and B2: aids enzyme production
  • Vitamin B1: helps to break down carbohydrates
  • Manganese, phosphorus, and calcium are essential minerals that all fish require

Recommended Foods

Omnivores can eat any of the foods we’ve included in the herbivore and carnivore sections of our guide. However, omnivores don’t need as much protein in their diet as carnivores, typically up to a maximum of 40%.

Commercial Fish Foods

There are many forms of dried commercial fish foods to suit different species of fish, including:

  • Flakes
  • Pellets
  • Granules
  • Discs or wafers

Flakes and pellets suit fish species that gravitate toward the top of the water column, such as bettas, whereas sinking wafers and discs are designed for bottom dwellers, such as catfish.

When choosing commercially prepared fish foods, always look at the ingredients list to make sure that the food isn’t packed with padding and contains high-quality foods. In particular, look out for whole meaty proteins, such as squid meal, shrimp meal, fish meal, earthworms, and Spirulina.

Homemade Fish Foods
spinach in a bowl

You can make your own fish food in your home kitchen. That’s a great way of ensuring that your fish is receiving the very best diet and can save you lots of money in the long run, too.

Others

There are some fish that don’t fall into any of the above categories.

Did you know that some fish eat wood?

Well, bizarre as it sounds, the Panaque genus of fish contains roughly ten species of wood-eaters, while the Hypostomus genus has almost 30. All of these fish rely on ingesting wood to supplement the rest of their diet. In fact, these fish graze on algae that they scrape from driftwood, consuming wood as they do so.

There are also several species of marine cleaner fish and some inverts that feed on the dead skin, microbes, and parasites that infect other ocean creatures. Some fish set up special “cleaning stations” where they hang out, waiting for customers to swim by. When a suitable fish arrives, the cleaner fish clean it, even venturing under the gill covers and into the mouth.

Species of cleaner fish include: 

  • Cleaner wrasse (Labroides dimidiatus)
  • Cleaner shrimp (Lysmata amboinensis)
  • Raphael catfish (Platydoras armalatus)

 These creatures are also scavengers, only supplementing their diet by cleaning other fish.

FAQ

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

Q: How often and how much should you feed your fish?

A: I always advise people to underfeed rather than overfeed their fish. 

Overfeeding can cause serious health problems for many smaller fish species, and uneaten food will pollute the water. Most fish species can be fed twice a day, although I recommend that you do plenty of research about the fish to double-check what their requirements are.

Q: How to avoid overfeeding your fish

A: Again, you need to research your fish carefully to learn their specific nutritional needs. 

As a general rule of thumb, you can feed your fish as much as they will eat in a couple of minutes. Some carnivorous fish only need feeding two or three times per week, whereas many herbivorous fish spend all day or night grazing on algae and plant matter within the tank.

Q: Do fish eat bread?

A: Although many fish will eat bread if you offer it to them, you shouldn’t do that. But why not?

Q: Do fish eat bread?

A: Although many fish will eat bread if you offer it to them, you shouldn’t do that. But why not?

Well, many of the ingredients in bread swell when put into a freshwater or marine tank. So, when the fish eats a piece of bread, the bread swells up inside the fish, causing bloating and constipation. If you constantly feed bread to your fish, he will become sick very quickly and could even die.

Bottom line: don’t feed bread to your fish.

Q: Can I make my own fish food?

A: Yes! You can make fish food in your home kitchen and freeze it in batches for later use. You can create recipes that will suit herbivores, omnivores, and carnivores. The process is simple, you don’t need any fancy equipment, and you can save yourself a whole lot of money by producing homemade fish food.

In Conclusion

Breeder is feeding colourful fighting fish in transparent square tanks

I hope you enjoyed our guide to feeding your fish. If you found the information helpful, please share the article.

Understanding what fish eat is crucial if you are to provide your pets with a nutritious diet that’s suitable for their natural eating habits. You can feed frozen or dry commercially produced foods, live foods, or make your own fish food at home.

Do you have any fish food recipes that you would like to share with other readers? Please note them 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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