What Do Carnivorous Fish Eat?

When I first started my fishkeeping journey, I found myself asking the same question that many beginners ask themselves: “What do carnivorous fish eat?” Today, I’m excited to share my knowledge and experiences to help you understand the dietary needs of these captivating aquatic predators.

It is our duty as aquarists to attempt to find the best foods that provide a complete and varied diet for our aquarium fish. We can break the feeding habits of fish into three broad groups.

1. Carnivore / Piscivorous: An animal that feeds on flesh / feeding on fishes.

2. Herbivore: Any animal that feeds chiefly on grass and other plants.

3. Omnivore: An animal that feeds on both animal and vegetable substances.

This article will focus on the carnivorous/piscivorous fish diet.

Besides the obvious differences of the diet groups i.e. meat/vegetable/combination, there are differences in what these foods contain in terms of protein, fats, mineral, etc.

Foods that fall into the carnivore group are naturally higher in protein and this tells us that if we are keeping a carnivorous fish species that we should be shooting for a high protein content.

The carnivorous fish diet should meet the following dietary guidelines:

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Protein: = over 45%

Fat: = min. 3%, max. 6%

Raw Fiber: = min. 2%, max. 4%

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Keeping these things in mind, feeding a diet to carnivorous fish is not hard to accomplish and providing live food is usually as simple as a five-minute exercise in the back yard.

What to Feed Carnivorous Fish

Carnivorous fish, as their name suggests, are primarily meat-eaters. Their diet consists of various protein sources, ranging from live prey to frozen or freeze-dried foods.

One of the most natural and nutritious options for carnivorous fish is live prey. This category includes:

• Feeder fish (guppies, rosy red minnows, etc.)

• Brine shrimp (adult and baby)

• Daphnia

• Bloodworms

• Blackworms

• Fruit flies (for smaller species)

Feeding carnivorous fish with live foods not only satisfies the fish’s natural hunting instincts but also provides them with essential nutrients and enzymes found in fresh prey.

1. Earthworms

A quick look under damp fallen leaves or a quick digging in the flowerbed will within minutes provide earthworms for feeding your fish.

Earthworms are one of the best things to feed carnivorous fish, and it has been my experience that most carnivorous fish will eat as many as you offer, provided they are of a size that the fish can handle.

Nearly all literature claims that the earthworm should be allowed to live in damp newspaper for a day or two in order to clean the intestinal tract. But honestly, I have never taken this precaution and have never had a bad experience.

Simple logic indicated to me that fish in the wild were not being served ‘cleaned’ earthworms and thus I never heeded the advice. You may wish to take this extra precaution. Avoid collecting worms from areas that could possibly be contaminated from any insecticides or herbicides that may have been sprayed in the area.

2. Mosquito Larvae

In the warmer months it is easy to find mosquito larvae or prepare a bucket to collect them. This is the one food that I have never had a carnivorous fish reject. They simply love the stuff and will attack at the surface to hunt the larvae down.

I always have a source going in the back yard during the summer.

The procedure I use to grow and collect them is to take a bucket that will hold 2-5 gallons and fill it with water. Throw in a handful of grass clippings or garden debris and place it in a shady area. Within a week or two you will have mosquito larvae.

In our part of the country we have Black Mosquitoes and the eggs are deposited on the water surface. The larvae breathe air and can be seen hanging from their air tube at the surface.

Often when you approach the bucket the larvae will dive to the bottom swimming in a jerking motion. They don’t stay submersed long and can easily be gathered with a fine net.

I always collect about every other day or two and if you don’t plan on collecting with this frequency, you may not even wish to start.

[su_pullquote align=“right”]Unattended cultures could easily allow thousands of mosquito larvae to become adults and become a nuisance in your area.[/su_pullquote]

Don’t forget to dump the buckets if you are going on vacation. If you are harvesting more than you can use the larvae can be frozen and used as a special treat for your fish or as conditioning food for spawning

I always try to have a supply in the freezer for wintertime feeding. I think it goes without saying that you should not feed more live larvae than will be eaten unless you happen to like that buzzing mosquito sound in the middle of the night and an itching sensation is something you can’t live without.

3. Ants and Small Insects

Ants will be taken readily by most top feeders, as will many other insects that you can collect outside. Small crickets are taken by my larger cichlids.

4. Beef heart

Beef heart is used by many and I have used this also.

Lately I have found that the time I use to prepare and clean the heart is not worth it when lean seafood is available at the seafood counter and requires no special cleaning before I feed it to my fish.

Beef heart must be cleaned of veins and fat and this can be a bit of a time consuming job. If you do plan to clean it I have found that if you initially cut it into wide strips and then place these strips in the freezer until they are just becoming firm but not frozen, the job is easier.

I have heard people say that beef heart is not good for fish but I have read no scientific evidence that supports either side. Their argument usually follows the lines that fish don’t eat it in the wild. On that comment I will beg to differ.

I have watched films of cattle herders in South America that will purposely sacrifice a steer in a river that contains Piranha. While the steer is being eaten, they drive the rest of the herd across at a spot 20 or 30 yards away.

All that remains of the sacrificed steer is bone and bits of pelt, it is obvious that the heart is eaten.

Also, in all the films of fish in the wild that I have watched, I have never seen flake food falling from trees or bubbling out of the riverbed, yet I would bet that these opponents to beef heart feed at least some prepared foods. However I would not make beef heart a primary diet for fish.

Other meats I have used with good results are cooked lean chicken, salmon, beef liver and turkey.

Some of these were not initially accepted but with a little time and patience your fish will acquire a taste for them.

There are foods that we can raise year round in the home and in a future installment we will take a closer look at them and don’t forget the many excellent frozen foods that are available from your aquarium shop. Some offer live foods and may be the route you wish to take to provide the varied diet.

I still think it is important to feed some flake or pellet food to the carnivore/piscavore. Even a pure piscavore will receive some plant intake if only that which is still in the stomach of it’s prey. There are vitamins and trace minerals that plants provide that cannot be found from any other source.

5. Other Alternative Foods for Carnivorous Fish

If you are in the midst of winter and collecting live foods is not possible there are many alternatives to be found with a walk through the grocery and at prices that will dwarf the cost of prepared foods.

1. A 6-ounce can of tuna packed in water can be purchased for 59-89 cents and my fish eat it with joy.

2. If your grocery has a fresh seafood department you can literally offer you fish a buffet of natural foods for a few dollars on the pound.

3. There are various fish species, clams, crab, shrimp, oyster and all kinds of seafood that can be used in the piscavore/carnivore diet. All of these can be frozen and small slices thawed and fed.

Many recipes exist for preparing homemade fish foods and most of them basically come down to putting in whatever is around, chopping or blending it and adding a little grain and gelatin to bind it, then freeze it and use as needed.

This works fine but I have often found that fish will eat the ingredient that best satisfies their taste and they allow the other ingredients to fall to the bottom and often remain uneaten. Where as, if I feed the ingredients one type per feeding, the food is more readily eaten.

Feeding Frequency and Portion Control For Carnivorous Fish

The frequency and amount of food you offer your carnivorous fish will depend on factors such as species, size, and water temperature. As a general rule, most adult carnivorous fish should be fed once or twice daily, with portions that can be consumed within 2-3 minutes.

Overfeeding can lead to obesity and water quality issues. You should monitor your fish’s intake and adjust accordingly.

Feeding natural is much more economical than feeding flake and pellet. I recently received an Email offering some ‘Premium Type Fishfood’. The price was $29.99 for 5 ounces. This is nearly $100.00 a pound.

Frankly, I feel that anyone who would purchase this is not an aquarist, they are an idiot. Save your money for more tanks and fish and at the same time you will be giving your fish an excellent varied diet.

Nutritional Needs and Feeding Tips

Carnivorous fish require a diet high in protein and fat to thrive. Here are some tips to ensure your carnivorous fish are getting the nutrition they need:

• Variety is Key: Rotate between different types of food to provide a balanced diet and prevent nutritional deficiencies.

• Observe Your Fish: Pay attention to how your fish eat and adjust the diet as needed. Some may prefer certain foods over others.

• Avoid Overfeeding: Carnivorous fish can overeat, leading to health issues. Feed them as much as they can consume in a few minutes, once or twice a day.

• Quality Matters: Choose high-quality foods to avoid introducing diseases and to ensure your fish are getting the necessary nutrients.