What do Fish Eat

What do Fish Eat? | Feeding your Aquarium Fish

If you are contemplating setting yourself up as an aquarist, you have most likely asked yourself, “what do fish eat?.” Well, fish will eat several things based on their natural environment, ecosystem, and a couple of other reasons.

Fish generally fall into these three broad categories: carnivore, herbivore, and omnivore.

Unlike we humans, fish cannot eat whatever they want based on their lifestyles. Whatever they eat is independent of their choices and mostly determined by their shapes of mouth, digestive tract, and teeth.

In this writing, our objective is to give you knowledge of what a fish diet comprises of from the wild to your aquarium based on the category your fish falls in.

What do Fish Eat:

1. Jellyfish

What do jellyfish eat

Jellyfish being carnivorous mainly eat protein-rich foods, and what else is richer in proteins than sea creatures? Their diet comprises quite a number of things such as copepods, fish eggs, and larvae.

Large jellyfish enjoy eating fish, shrimp, and crab. Interestingly enough, larger jellyfish eat other jellyfish!

Whenever a bloom appears (a group of jellyfish swarming together) then you are in for some big trouble as they can eat any and everything in the water. This may cause problems for other fish as no more food will be available.

Fun Fact: Did you know that jellyfish do not have a heart or a bone?

In case you are wondering how boneless, brainless, and even heartless (yeah, literally heartless) creatures like jellyfish can eat other fish, then here is the answer. Jellyfish possess long tentacles hanging from their bodies useful for trapping their prey.

At times, the venom from these tentacles is used to kill the prey first. Once captured, the prey is brought to the jelly’s mouth by the use of oral arms.

With a proper jellyfish tank, feeding jellyfish while ensuring their safety should not be much of a struggle.

2. Crayfish


Crayfish are omnivores and therefore can eat possibly anything from plants to proteins. In the wild, their main diet comprises decomposing animal matter and decaying vegetation.

This is mainly attributed to how easily such kinds of food can be found in the wild and also the ease of ripping the food apart using their claws.

They also fancy small live fish. However, this is easier to find in the aquarium than in the wild as there is all the space in the wild for the fish to escape to.

At times, this fish can cannibalize its species and even live plants.

They are not particularly the best swimmers in the wild, therefore, they tend to wait for their food to settle at the bottom before they feed. They then use their claws and their first pair of legs which have small pincers modifications, to pick up the food and eat it.

In the aquarium, they are likely to go after your plants, algae, and vegetables. Therefore, ensure that you plant fast-growing and hardy types of plants like moss to survive with the crayfish. Balance this with meat and protein-rich foods as they are important for fast growth.

Pellet-type foods such as shrimp pellets may come in handy as they quickly sink to the bottom making the food available to the fish. If you can avail them with small live foods such as small fish and shrimp, you could make their diet a little bit more interesting.

Interesting feeds to give your crayfish include algae wafers, krill, aquatic plants, and live small fish. Blood worms, meat, daphnia, mosquito larvae, dead fish, shrimp, fish foods, shrimp pellets, frozen foods, snails, fruit, squid, insects, and vegetables.

3. Starfish

Starfish 2

Starfish are carnivores hence fancy protein-rich foods sourced from other animals. Since starfish are very small movers, they devour other slow-moving animals too.

Some of the things that make up their diet include; sponges, clams, oysters, sand dollars, coral, and mussels. Besides the fact that their prey is slow movers, they also attach themselves to rocks the same as them making it easy for the starfish.

Some larger starfish also feed on other animals such as fish, especially injured ones that aren’t able to get themselves out of the danger in time. Dead fish and plants decomposing on the beach form part of the starfish’s diet.

I couldn’t help but talk about the mode of eating this fish uses to eat. Their feet have suction cups on the bottom to help them hold on to the prey.

Once a good grip on dinner is established, they will use their feet to open the oyster or clam. After this, the fish’s stomach surprisingly comes out of its mouth and drags itself into the shell of its prey.

The stomach then surrounds itself with the edible parts of its prey and digests it into juices. It is only then that the stomach retreats into the mouth. Just phenomenal.

See also: Is seiryu stone good for aquarium?

4. Goldfish

gold fish

Goldfish are omnivores in nature. Several foods can be fed to goldfish but they are affected by certain factors. Let’s look at the specific food versus the factors.


Your goldfish can swallow air while feeding on flakes or floating pellets off the surface of the aquarium potentially resulting in indigestion problems. Flakes also tend to lose part of their nutritional value after the tub is opened and the flakes exposed.


Unlike flakes, pellets retain their nutritional value more than flakes. However, pellets can be too long making it impossible for smaller or younger goldfish. Also, sinking pellets may be tedious to find and remove.

Rotting these pellets at the bottom of the water may result in pollution of the water. It then becomes obvious that this is the advantage of floating pellets.

Live foods

This is available in most pet stores in the form of brine shrimp, tubifex worms, daphnia, and aquarium snails. These are a great source of protein and also replicate how hunting in the wild would be for the goldfish.

The only challenge with this is that you put your waters at risk of diseases from the introduction of these live fish from pet stores.

Freeze-dried foods

This offers a rich protein source while canceling the risk of the introduction of diseases into your water.


Adding a little vegetable here and there will go a long way in improving the immunity of your goldfish.

See also: Pothos plant in aquarium

5. Bettas

Betta fish in aquarium

If you are asking yourself the question, “what do fish eat?” and you are looking to grow bettas, you shouldn’t fret because bettas are naturally carnivores. This means that they fancy and prefer food rich in protein.

In the wild, they often find insects and insect larvae a great part of their diet. In an aquarium setting, things aren’t so much different.

Pellets and flakes made from the fish meal are great options for betta fish. Frozen or freeze-dried bloodworms and live brine shrimp make excellent supplemental food for this fish and also hasten the process of breeding.

6. Clownfish

What do clownfish eat

This fish is just so fun and easy to feed. This is the major reason why it is such a good deal for beginners. They are omnivores in nature.

In the wild, they tend to eat copepods, fish eggs, larvae, anemone tentacles, algae, and small crustaceans. These protein-rich foods can also be replicated in an aquarium setting by offering them Mysis shrimp and brine shrimp.

Your clownfish also won’t mind frozen fish and finely chopped table shrimp.

Live foods are also important in replicating the natural setting vital for breeding. If your tank is clean of algae, then flakes and pellets that have spirulina will offer the vegetable end of their omnivore diet.

Small clownfish require to be fed close to their safe zones, a spot where they feel comfortable until they are larger. Even when large, you will need a specific spot to protect them from strong water flow that may hinder their process of feeding.

Adults need to be fed twice a day while the juvenile requires at least 3 eating windows. Just give the fish enough food that it could comfortably eat within three minutes. Ensure to clean any leftovers from the water to maintain the water at the optimal range.

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What do fish eat in the ocean ?

The ocean is a vast mass of water, calm at times, and stormy at others. The ocean possesses countless species of fish and plants. Some have already been discovered and studied by scientists while others are yet to be identified.

Here, we shall focus on the known to clearly understand what they eat while under there.

In the ocean, most fish eat other fish for survival. Others fancy plankton while others will sweep each and everything on the floor of the ocean.

To begin with, the fish diet is diverse: some are meat-eaters who enjoy marine animals such as small fish, crustaceans, and worms. Others eat plants and small organisms while others are predators that hunt down other fish. Therefore, a fish diet will depend on its classification.

Fish can be torn down into three groups

  • Omnivores
  • Herbivores
  • Carnivores

Omnivore fish can survive even in the toughest of times as they can eat anything in the ocean. Their diet comprises crustaceans, worms, and small fish among other things that aren’t poisonous to them.

These fish cannot simply die of hunger in other oceans for if bad goes to worse, they can even eat algae and detritus which includes coral mucus and other organic substances.

Carnivore fish go hunting for other small or injured fish for their daily meals. They tend to use surprise attacks on prey and maim eat before using their mouths to feed. They have special modifications that aid this.

What do fish eat in the wild ?

As we have seen earlier, different fish will eat different foods based on the category they fall into; whether herbivores, omnivores, or carnivores. Therefore, these questions tend not to be that straightforward to all the fish, rather they will depend on a specific fish.

However, generally, the most common things that fish eat in the wild are:

  • Insects
  • Larvae
  • Algae
  • Worms and leeches
  • Crustaceans
  • Other fish

Some fish will tend to eat a lot more protein than others and find stuff like algae cool for them. This all depends on the nature of the environment the fish is in.

What do fish eat in the pond?

Feeding fish in pond

A good number of pond fish are omnivores, therefore will eat almost anything in the pond. A good sample would be koi and goldfish. These two species will eat squash, spinach, wheat germ, plankton, shrimp, algae, peas, and even citrus fruits.

The diet of a fish in the pond will also be determined by the water temperature. In warmer waters of any figure above 60 degrees Fahrenheit, the fish’s metabolism is quite high and therefore will require protein-rich foods.

In waters below 60 degrees Fahrenheit, a diet lower in proteins and higher in veggies will be preferred as their metabolism is slower and the fish won’t need as much energy.

What do fish eat in lakes?

What do fish eat in the lakes? Well, in the lake setting, without all these supplemental foods in the market, fish still have quite several foods at their disposal.

The goldfish, for instance, is a very opportunistic eater and will feed on plants such as the duckweed and water sprite, insects, and aquatic invertebrates such as tadpoles and mosquito larvae.

Larger species of fish may also find eating smaller fish interesting. Wild koi, in particular, will often fancy aquatic insects, small fish, algae, plants like water lily and water lettuce, frogs, and snails.

And what do fish eat at the bottom of the lake? Bottom feeders fish browse at the bottom of the lake most of the time looking for any edible food down there.

Koi fish are bottom dwellers that use their sensitive facial barbels to locate food at the bottom of the tank. Things that they normally find include snails, shrimp, insect larvae, dead fish, and even sizeable fish such as salmon and flounder.

See also: Can koi fish live up to 200 years ?

Sturgeons in the wild can grow to a massive size of even 100 pounds or more. This site requires a significant amount of food to maintain. This is why they will eat almost everything in the lake.


Food and Agriculture Organization (FAO): FISH FEEDS AND FEEDING

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