What do fish eat? Can I make my own fish food?

The fish in the ocean, in freshwaters and those kept as pets are so diverse. Fish consist the majority of marine life and yet, there are still some small details that we do not know about them. For one, have you ever wondered as to what fish eat? Or are there carnivore or herbivore types of fish too? 

What do fish eat

Dolphin hunting.

In this post, we answer the question, what do fish eat. If you are a pet fish enthusiast, or just a person who is curious about this, sift through this post and read on.  

What do fish like to eat? 

There is no one answer to this. The diet of fish always depends on their environment, size, and biology, in general. There are some who feeds on smaller marine life while others are just contented on sea grass and algae. The bulkier ones tend to be more carnivorous while some others are omnivores. 

The question what do fish eat is quite important in conservation talks. Unregulated human activities in the seas and rivers have a ripple effect on the diet of fish. 

How do fish forage for food? 

Millions of years of evolution perfected the different ways of food getting for fish just like all else in nature. Fish have precise and highly attuned senses which help them in foraging for food. For instance, those fish who live near water surfaces have a daylight visual acuity and color vision. 

On the other hand, those that are considered deep-sea fish have a vision range that is more adaptive in low to no light spots. Other than these, fish also have an evolved echo-location. This means that they can localize sounds underwater. This further means that they can locate food through their ability to detect pressure gradients and motions underwater. 

The ways in which they forage food also depend on their size, biology, and behavior. For example, predatory fish (which are also mostly carnivores) enforce stealth and speed in getting food. 

On the other hand, those who are herbivores are most likely found among coral beds or in seagrass beds. Those who are considered bottom feeders are foraging in the sea floor scouring for morsels left by other marine creatures. 

What does wild fish eat?

Fish in the wild are mostly omnivores. Wild fish do not have a specific diet pattern since they practically eat whatever is available in their habitats. Marine biologists comment that 40-50% of the food wild fish eat are high in protein and carbs. 

Case in point, wild fish feed on crickets, grasshoppers, flies, midges, leeches, worms and nightcrawlers, among others. Larger wild fish on the other hand, eat mice, baby snakes, turtles, frogs and other small fish. Those that are bulky like sharks, are predators to sea lions and seals, other larger fish as well as birds. 

What does fish in the ocean eat?

Ocean fish have more diverse food types to choose from. The following are the most common food which ocean fish consume: 

  • Zoo plankton
  • Sponges
  • Fish larvae and eggs
  • Worms
  • Jellyfish
  • Crustaceans and floating insects
  • Algae and seagrass
  • Other fish

What do baby fish eat? 

Generally, baby fish would eat the same food as what adult fish would eat but on a more limited scale. As soon as they hatch, they would start feeding on algae, insects, small crustaceans and worms. As they swim around, their natural instincts lead them to other small preys. 

Baby pet fish on the other hand must be fed with premium quality flakes or pellets. If you want to start them with live food, zoo planktons and small shrimps are the best choices. Also, they need to be fed many times a day. Never introduce new food source to baby pet fish without the go signal of your vet. 

Are fish omnivores?

Not all fish are omnivores but majority of them are omnivores. They can eat both plants and meat. However, if you keep them in an aquarium, make sure that the pellets you feed them have the complete nutrient requirement that they need. 

What should you feed your fish? 

Just as other living things, fish also need a good balance of nutrients for them to survive. They have to be fed with carbs, proteins, minerals, and fats, among others. However, the amount that they should consume must depend on the type of eaters they are. 

Herbivore fish

Herbivores are plant eaters. They have no true stomachs and they have long but small digestive tracts which means that they have difficulty in digesting meats. As such, their diet is fiber-based. This is the reason as to why biologically, they have very long digestive tracts. 

Case in point, herbivore fish’s diet includes algae, plants, even vegetables and fruits. They need fibrous foods and at a frequent manner because they only have their intestines to break down their food. 

Herbivore fish usually have flat teeth. This helps them to finely grind their food before they swallow. In the wild, they feed on algae, plants and other sea vegetables. Some examples of herbivore fish include parrotfish and sturgeons. 

Marine biologists say that there are not true herbivore fish because all fish need a certain amount of protein for their balanced health. Nonetheless, they are important in maintaining the water’s ecological balance because they keep the algae level and corals in check. 

Carnivore fish

The staple food of carnivore fish would be meat and protein-rich food. Either live or just carcasses, carnivore fish love to eat meat. Some of the most popular carnivore fish would be piranhas, killifish, pipefish, betta fish and arowanas. 

Carnivore fish are identifiable for their large mouths and sharp teeth. Anatomically, they also have larger stomachs and digestive tracts. As carnivores, they either actively chase their preys or work as scavengers. 

A carnivore fish’s diet is 70% composed of protein. They also need 30% of fats to sustain their agility and vigor. As such, in the wild, they would often feed on smaller marine life, including crustaceans, insects and live fish. When kept in an aquarium, say in the case of betta fish, they are often fed with frozen fish food. 

Omnivore fish

Basic science defines omnivores as those that consume both plants and meat. This is so because anatomically, they partly have the traits of the digestive track of both carnivores and herbivores. A popular omnivore fish would be the batfish. 

Omnivores are considered as the easiest fish to handle. This is so because in a controlled environment, you can feed them with anything. Nonetheless, all nutrient requirements (i.e. protein, carbs, fats and fiber) should be present in the pellet or flake of your choice. 

Food for pet fish

Because they are in controlled environments, hence, they need special food to remain healthy. They also need specific nutrients to survive their controlled environments. As is the case, you should always consult your local vet about the best pellet type for your breed of pet fish. 


Nonetheless, the usual fish food is composed live food, greens, and freeze-dried food. Others would include freeze-dried krill, shrimps, worms, planktons, and prawns. The most common dried fish food would be flakes and pellets. They are infused with different formula depending on the fish. 

If you intend to feed your pet fish with live food, the safest choices include crickets, worms, feeder fish and ghost shrimps. You can also feed them with pellets and live food alternately but make sure that you have consulted with the vet or local fishery first. 

Pellets vs flakes

Flakes and pellets are the two major food categories for pet fish. Flake fish food comes in two varieties: the marine flake food and the tropical flake food. Marine flake food is specifically manufactured for fish breeds with saltwater diet. 

On the other hand, tropical flake food is for freshwater fish breeds. Some breeds like the goldfish, betta fish, and cichlids consume a specific type of flake fish food. Flake fish food is easier to use compared to pellets. They are simply sprinkled on the water and you would not have to wait for them to sink. 

Pellets vs flakes

Meanwhile, pellets are also manufactured to meet specific nutrient requirements of different fish breeds. They can either be sinking or floating pellets. This type of feed is more advisable for larger sized fish breeds. This includes cichlids, oscars and groupers. 

You have always remember, however, not to feed pet fish with too large pellets as it could cause indigestion and even death. 

Frozen food

This type of food is used as supplement for either flakes or pellet. They enhance the nutrients that fish pets receive especially if they need more protein. Frozen or freeze-dried food includes krill, bloodworms, and plankton. 

Frozen food for fish is very accessible and can be kept in the freezer for a long time. They are even considered as better food alternative compared to live food since the latter may transmit parasites and bacteria to your pet fish. 

Do fish eat bread? 

For some reasons, bread morsels are fed to pet fish. But this should be corrected because this is unhealthy. Bread expands the digestive tract of the fish. Also, they cannot process all the ingredients of bread. This would lead them to serious discomfort. For this reason, feeding them with bread can lead to constipation or death. 

How often and how much should you feed fish?

If you want to be a good pet fish owner, you have to remember to feed your fish little but at a more frequent manner. Never overfeed your fish because it leads to a lot of adverse effects. Some of these would be changes in water quality, and fatalities on the fish themselves. 

Moreover, overfeeding could lead to food rot in the fish tanks. Not only are you allowing waste accumulation but it also affects the oxygen quality in the aquarium. Low oxygen levels in their environment affect fish because they induce fatty liver, fin rot, and flatworms. Clogging of aquarium filters are also an effect of overfeeding. 

How do you avoid fish overfeeding? 

The common behavior of fish is that they start swimming around the tank when they see humans approach. For the unknowing, they may seem hungry but usually they are not. Given this, how do you avoid fish overfeeding? 

How do you avoid fish overfeeding

The first thing to consider is the breed of fish that you have. Note that in their natural habitats, there is no feeding schedule and they could just graze all day if they want to. Nonetheless, as per rule of thumb, it is advised that fish be fed at least twice a day. 

Also, they must be fed continuously for a duration of five minutes. After that, remove all the left overs so that the water quality would not be altered. 

Can I make my own fish food? 

There is a risk to feeding fish live food because of the parasites and bacteria that might be transmitted. But yes, you can make your own fish food. As a matter of fact, hobbyists with a steady supply of live food tend to culture their own fish food. 

Some of the most common live fish food cultured for DIY feed would be the following: 

  • Grindal worms
  • Gel food
  • Brine shrimp
  • Blackworms
  • Daphnia
  • Aquarium snails 

Can fish acquire bladder issues? 

Yes. As a matter of fact, swim bladder illness is one of the most common diseases of pet fish. It is a usual occurrence for newbie fish handlers which, if mistreated could become a permanent disease. When the swim bladder is affected, irregularity in swimming motion is evident. 

Final thoughts

The diversity of fish breeds calls for different food types. In so far as salt and freshwater fish who are in the wild or their natural habitats, the type of food they eat depend mainly on their size, environment and biology. 

Pet fish on the other hand, have more specialized needs due to their controlled environment. Nonetheless, they are still not picky eaters as long as their dietary needs are supplied.  

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