What Do Fish Eat?

We know that man and some other animals eat fish but what do fish eat? The word fish is an all-encompassing term used to describe most aquatic organisms such as ray-finned fishes, sharks, whales, lampreys, and coelacanths, to name a few. Besides being an aquatic organism, fish is a major source of protein to man. As a matter of fact, statistics provided by the Food and Agriculture Organization show that fish alone constitute 16% of the total protein consumed by man.

Judging by such statistics, one fact is clear – fish is very significant to man, and as such, activities like fishing or fish farming are capable of offering a huge string of income to its proprietor. It is, however, imperative to know that besides being a good source of food and income, there exists a huge percentage of people who keep pet fish. Irrespective of the reason why we love them (either for farming, fish keeping, or consumption), it is imperative we know what fishes eat, as no knowledge is lost. What do fish eat in their different habitats? Let’s enlighten you.

What Do Fish Feed On In A Pond?

A pond is a small still body of water that is formed naturally or artificially and used majorly in fish farming. Types of pond fishes are goldfish, koi carp, catfish, etc. Most pond fishes are omnivores and are open to a wide range of diets. That being said, there are four categories of what pond fish feed on.


For most fishes to survive, they require a certain level of protein (usually high in amino acids). As a result, it is good to provide pond fishes with food rich in protein. This protein can be derived either from animals or plants. Pond fishes like goldfish and koi are capable of eating insects, flies, small snails, tiny fish, silkworms, and blood worms. A major component of protein plant-based feed is water lettuce and water lily. While younger fishes require more protein in their feed, it is imperative that it is introduced in bits as excess might lead to several complications.

Carbohydrates and Sugars

Fishes like every other living organism require a certain level of energy to carry out their activity efficiently and effectively, and as such, it is required that carbohydrates constitute 10% of a pond fish diet. That being said, it is important to give pond fish the required level of carbohydrates by giving them food like raspberries, broccoli, shelled peasants, etc.


Fishes with a low level of fats in their diet tend to have stunted growth and deformity. Besides being a strong supplier of metabolism in fish, fats also serve as nature’s insulator. Hence, it is important that you feed your pond fish with food rich in fats like brine shrimp and soybean meal.

What Do Fish Eat in The Ocean?

The ocean, besides being a huge body of water, is a natural habitat for several plants and animals like fish. Fishes in the ocean can be grouped into three classes which are herbivores (plant eaters), carnivores (flesh-eaters), and omnivores (plant and flesh-eaters). A typical example of herbivorous fish is rabbitfish, parrotfish, and damselfish. They are known to eat plants like turfs, sargassum, and fennel weed, to name a few.

Carnivores, on the other hand, are fishes that eat small fishes, insects, crustaceans, and larvae. Since most carnivorous fishes are predators, they possess sharp pointed teeth that give them the added advantage when chasing prey, examples being piranha, hatchet fish, tuna, etc. Although carnivores can eat plants if they desire, they can’t derive any nutrients from them as their digestive system isn’t built to digest vegetables.

There are fishes in the ocean that can be classified as omnivores on the other hand and they have the ability to derive nutrients from meat and vegetable matter and, as such, consume a wide range of food. Examples of omnivorous fish are freshwater angelfish and barb.

Do Small And Big Fish Eat The Same Food?

Yes and no. Based on their feeding pattern, fish can be grouped into three classes, which are herbivores, carnivores, and omnivores. From that classification, it can be further deduced that fishes in the same class eat basically the same thing. However, the diet of a fish is based on more factors such as water temperature, breed, and size.

Hence, small and big fish might eat the same food, but in different quantities, as small fish require more food with high protein content than their much older counterpart. For some omnivores, small fishes tend to eat only animal diets and begin consuming plants when they increase in size.

What Kind Of Food Can You Feed Your Pet Fish?

A goldfish feeding in the ocean source

After establishing that different fishes consume different kinds of food, we must understand that feeding your pet fish is a different thing altogether. There is a plethora of commercially prepared fish food that is commonly used for feeding pet fish. They include:

Flake Fish Food

We have flake food for all kinds of fish. Tropical flake food is specially made for freshwater fish living in groups (referred to as community), while marine flake food serves the dietary needs of the saltwater fish. Cichlids, bettas, and goldfish shouldn’t be exposed to generic food as they have their own formulated flake foods specially made for them. When it comes to pet food diets, flakes are among the easiest, just sprinkle the surface of your fish pond with a few flakes and watch as the fishes swim up to the surface to feed. However, you should guard against overfeeding.

Read Also: Details of the Differences Between a Turtle and Tortoise

Pelleted Fish Food

This kind of fish diet comes in a sinking or floating variety and is prepared to satisfy the dietary requirements of some specific kinds of fish. Pellets are best suited for larger breeds like groupers, oscars, and cichlids. Ensure that the pellets are not too big for the fish as it can result in severe indigestion issues.

Frozen, Freeze-Dried, and Live Foods

Frozen and freeze-dried foods include brine shrimp, bloodworms, plankton, krill, and many more. All these make wonderful treats that can be used as supplements in a regular fish diet. They can be bought from pet stores in your locality and preserved in the freezer. These tasty treats can be enjoyed by your pet fish, but your best bet is to go for the frozen or freeze-dried varieties. This is because; a fish can get infected by eating live food such as worms.

Other Treats for Fish

Having done justice to the question of what do fish eat, we still have a few tricks to share with you in that respect. If your pet fish falls under the omnivores or herbivores groups, you might consider feeding with spirulina, which is highly nutritious. Seaweed is commercially prepared in dried sheets and can be purchased from pet stores and fed to your fish, but you must apply caution.

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