What Do Fish Eat in the Wild and Ocean?

When someone asks “what do fish eat?”, usually it sounds like a simple question. However, with over 30,000 species of fish in existence and many yet to be discovered, one cannot but wonder how these creatures feed. With different species of fish and many existing in different parts of the world, their diet often varies.

However, there are 3 major categories of fish. Therefore, to determine the diet of a particular fish, the category it falls into must be determined. Read on to find out more about the 3 major categories of fish.

1. Carnivores

Carnivorous fish survive on a meat-based diet. They eat other fish, snails, mollusks, crustaceans, and even insects. Depending on the species, some fish are very active hunters. They are known to hunt for their prey. However, some other carnivorous fish patiently wait for their food to come to them. An example is the anglerfish. This fish uses a lure found on its head to gather smaller fish.

A common feature of carnivorous fish is their large month. Fish such as bass and groupers are examples of fish with this feature. Another feature is their large teeth use for tearing their prey apart. They also have an aerodynamic body that helps them swim faster in the water.

Although the majority of carnivorous fish tend to hunt for their food. Some other species do not, and often scavenge from active hunters. Examples include catfish or loach, eating debris, dead fish at the bottom of the water. Their scavenging activity helps keep the water clean.

2. Herbivores

Like any other herbivore, these kinds of fish survive on a plant-based diet. Their diet often includes algae, seaweed, seagrass, phytoplankton, corals, and other plant life. In the wild, they often graze, looking for plant life to feed on but in aquariums, fruit and vegetable matter are usually fed to them.

They find their food source on woods, rocks, or other areas of the sea that have grown algae and any other sea plant. Usually, they have flat teeth or beak-shaped mouths. This helps them eat algae off surfaces.

Although herbivore fish exist, it is rather difficult for fish to live on a plant-based diet alone. Most fish need a balanced diet that includes both plant and animal-based food. This makes herbivore fish a rather rare species of fish.

Some pet stores have herbivore fish you can buy. However, you should note that they are hard to keep as they need to be fed constantly else, they starve.

3. Omnivores

This is the most common category of fish you can find. They live on both animal-based and plant-based diets. Depending on the species, some fish might need a larger percentage of animal-based diet than plant-based, while some might require more plant-based meals. It is advisable you find out these details before getting a fish as a pet.

They make for great pets as they are easy to manage and usually can eat anything offered to them. You can feed them protein-based food like shrimps, frozen food, freeze-dried food, and some even enjoy hard-shelled seafood like crabs.

Having figured out the major categories of fish that exist. Below, you will find out what some fish eat. Read on.

What do Koi Fish eat?

Just like humans, Koi fish are omnivores with the ability to eat plants, bugs, algae, and also smaller fish. However, their diets need to be made up of a variety of nutrients to keep them very healthy.

Koi fish in the wild know how to take care of their meal. They feed mostly on proteins, and some minerals, vitamins, fat, and carbohydrates.

In ponds, they need to be fed occasionally. Koi are not picky eaters and can eat almost anything humans can eat. Food such as fruit, vegetables, shrimp, and the likes can be fed to them. However, foods high in carbohydrates are not advisable as they can be hard on their stomach

If you have an ecosystem pond, feeding them might not be for survival. Nonetheless, you can feed your koi fish occasionally just for fun or to make them grow bigger. Also, koi fish eat according to their size, so before buying fish food, you should take note of the size of your fish. Bigger Koi would prefer pellets and smaller ones would only eat flakes or small-sized food.

Below are some food items you can feed your koi fish:

Wheat Germ

This is not some kind of harmful germ that comes from wheat. It is just what seeds of the wheat plants are called. Wheat germs are a great source of nutrients for koi fish and they can help them grow faster. It is rich in vitamin E which is aids blood circulation in koi fish, also increases oxygen flow, and improves the immune system. This food is easier to digest in colder months when koi fish digests food slowly.

Brine Shrimp

Koi fish need lots of protein to stay healthy and grow well. Brine shrimp is a great source of protein for your fish. It also contains other nutrients essential for your Koi fish. Freshly hatched Koi fish need enough protein to grow adequately. Brine shrimp is also great for adult koi fish during the summer months when they are more active.

Spirulina Algae

The Spirulina (or Cyanobacterium) is a bluish-green alga commonly found in hard water that has a naturally high PH level.  They have the ability to makes their own food, and only grow up to half a millimeter. Koi fish gets lots of benefits from eating these algae. It aids digestion and enhances immunity in Koi Fish.

Fish Food

One thing you can readily get your hands on in the market is fish food. Luckily, Koi fish also enjoy processed fish food too. The size of your Koi fish would determine the type of food to get.

Powdered food is suitable for small koi while pellets are okay for average-sized koi. These foods usually contain the essential nutrients like proteins, vitamins, and fats that your koi fish needs.

What do pufferfish eat?

Pufferfish are such an interesting breed with their peculiar personalities, one of which is begging for food from their owners. They are omnivores and just like humans enjoy varying diets. However, if you are thinking of having pufferfish at home, you should note they enjoy household foods. They do not care much for processed fish food.

Here are some food pufferfish eat


Their teeth are big, sharp and surprisingly never stop growing. For this reason, they need hard-shelled seafood like crabs, clams, etc. This helps them maintain the teeth by filing them down so they don’t grow too long. Also, pufferfish find crustaceans really tasty and regularly snacks on them. They contain essential nutrients that help the fish grow.

Frozen Fish

When they do not have access to live fish, pufferfish equally enjoy frozen fish. Fish like salmon gives good nutrition especially for fishes in the aquarium as it supplies carotenoids that help maintain color. However, remember, pufferfish need crunchy food so, making fish their only diet is not a great idea.


This is another great puffer food that is readily available at grocery stores. It packs a lot of nutrients that will help pufferfish grow. However, just like frozen fish food, it doesn’t have any hard parts for the puffer to crunch on. This makes it not a suitable steady diet for the fish.

See also: How to Tell if Fish is Bad?

What do betta fish eat?

Betta fish are quite popular in the fish world and among aquarists. Also commonly referred to as Siamese fighting fish, these fish have bright colors and pretty fins. They are carnivores and in the wild are known to eat small crustaceans, insect larva, and sometimes tiny fishes. Although they sometimes eat plants, they cannot survive on this as they need a diet rich in protein.

If you have or want to have a betta fish as a pet, then you should know what they eat and how to feed them. This is important so as to maintain the good health of your fish and also make sure you are not overfeeding them. Overfeeding in fish usually leads to gastrointestinal issues. You need to feed your bettas at least twice per day

What do fish eat in the Ocean? What Do Fish Eat

The ocean is home to various animals as well as plant life. The diet of a fish is dependent on its species and most importantly its size. Just like humans, fishes can be herbivorous, carnivorous, or omnivorous. However, most fishes are omnivores.

Often, carnivorous fish prey on smaller fishes and other marine lives such as worms, crab, prawn seals, sea lions, lobster, etc. Smaller carnivore fishes often hunt in packs, taking on their prey as a unit. Herbivores as the name imply mostly survive on marine plants mostly found at the bottom of the ocean. These include algae, seagrass, corals, phytoplankton, etc.

To get more information on what fishes in the ocean eat, let’s take a look at some of the well-known fish species and find out what they eat.


The Diet of this fish varies according to the species. However, they mostly eat animals such as fish, crustaceans, mollusks. They are also known to eat marine mammals like seals, dolphins, porpoises, and even larger fishes like tuna, mackerel, and small whales.

Typically sharks consume any type of sea creature. However, it is observed that each species of shark has a preference for different prey. Squids are favorite to Blue sharks, while Tiger sharks love to eat turtles. Hammerhead sharks love to prey on rays. Some bigger species of shark eat plankton choosing them over meat.

Sharks can eat their prey whole or cut them into chunks with their very sharp teeth.


They are often found in tropical areas, near shores or coral reefs and there are about a hundred or more species of snapper. Some of the known species include yellowtail snappers, emperor snappers, dog snappers, bluefish (the commonest member), and dog snappers. The sizes of each species vary, however, there is not much difference when compared.

Snappers are carnivores. Although young snappers often start off by feeding on plankton, they soon grow to be hunters. Adult snappers eat small fish, mollusk, and crustaceans. This species of fish shares habitat with sharks, morays, barracudas, and jacks. So, they get preyed upon by larger carnivorous fish


Rays can be found in various parts of the world. They are carnivores and are known to feed on various sea creatures. Hunting techniques vary according to the species of this fish. Some specie has sting just below their tail which can be used in catching preys, while electric rays stun their preys with electricity. Rays are mostly found at the bottom of the sea. However, some can be found near shore.

Larger rays are mostly filter feeders, while smaller species feed on oysters, clams, snails. Often hunting for their prey at the bottom of the ocean.


Often found at the bottom of shallow water, some species of the scorpionfish have been found two kilometers to the ocean floor. They have beautiful feathering fins that come in a range of colors. The fins contain venoms that can be used to stun prey.

They are omnivores and so need a lot of protein-based food. Some of their prey include small fish, mollusks crustaceans, and some other creatures that live well below the ocean.

What do fish eat in the sea?

What do fish eat in the sea

Most fish in the sea are omnivores that tend to consume both plant and animal-based diets. They can be active hunters preying on smaller sea creatures or scavengers living on whatever they can find at the bottom. Although few, some species of fish are herbivores, living completely on plant life.

Can fishes eat bread?

It is common to see people feeding bread to fish at public ponds. Sometimes, when you run out of fish food, you might have fed some bread to your pet fish. However, you should know bread are not a healthy food for fish and it should not be fed to them.

Although they might eat bread if fed, it is not a healthy meal for them. The digestive system of fish is not as complicated as that of humans and cannot really process bread well. This can cause serious discomfort in fish and ultimately shorten their lifespan.


In this article, you can find an adequate answer to the question “What do fish eat?”. Some fish species have been discussed and details of what they eat have been revealed. All fish do not eat the same thing.

Some fish are omnivores eating just about anything that comes, some are carnivores, very active hunters, preying on other sea creatures. Very few are herbivores.

So, if you plan to get a pet fish, we advise you know the category it falls to so as to know what and what not to feed it.

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