Do Cardinal Tetras Eat Algae: A Close Look at Their Diet

Cardinal tetras are some of the most popular freshwater fish in home aquariums, but it is important to be aware that they have specific dietary needs. Cardinal tetras need a varied diet that includes both meaty and plant-based foods. Moreover, some owners also believe that Cardinal fish also eat algae. Is it true?

Do Cardinal tetras eat algae? Yes, Cardinal tetras eat algae, but not to the extent that most owners think. They only nibble the algae present on some loose pieces found in plants, rocks, and driftwood. They are not good at eating algae from the walls of your tank and cleaning the aquarium glass.

Cardinal Tetras have a voracious appetite. They will quickly devour any food you give them, including plant-based foods such as lettuce or spinach (but remember to blanch all that food first). They also like proteins rich in fats like brine shrimp and bloodworms.

In this post, we will deal with the algae-eating behavior of Cardinal tetras and know more about their diet.

Do Cardinal Tetras Eat Algae?

Yes, Cardinal Tetras eat algae, but it is not their primary food source. Mostly, these fish will only eat algae if the other food is not available. Thus, they are not like Siamese Algae Eaters who will constantly eat algae, but they enjoy munching on it when food is scarce.

Moreover, Cardinal tetras are not picky eaters. Cardinal tetras will consume a variety of food, including brine shrimp, blood worms, and daphnia. As juveniles, they enjoy algae wafers to supplement their diet with green veggies. Still, adults can survive on a varied omnivorous diet mainly consisting of plant matter such as zucchini slices and peas.

Why Do Cardinal Tetras Eat Algae?

Cardinal tetras usually feed upon the food they can find in the wild. However, they will eat live foods, flakes, and pellets in the tank that the owners give them. Cardinal tetras are not picky when it comes to their diet.

But there are some specific reasons why Cardinal tetras eat algae:

When There In No Other Option Of Food

Cardinal tetras will often eat algae in the tank because there is nothing else to eat. They are schooling fish, and it’s not likely that they would want to be alone in a tank without any company or food for very long. So Cardinal tetras often go for the first food source that they see.

When Cardinal Tetras Are In The Juvenile Stage

Cardinal tetra fry will eat algae when there is nothing else to feed them because it’s a natural part of their diet in the wild. If you have a breeding pair, then one day, you might look into your tank and see baby Cardinal tetras swimming around. Cardinal Tetra fry will eat the same things that their parents do, even if it’s algae in your tank, instead of bugs or fruit flies as they would find in nature.

When Cardinal Tetras Are New To The Tank

It can take Cardinal tetras a few days to settle into their new tank and eat the right foods. Until they figure out what is safe for them, Cardinal tetra’s will eat anything they can find in or around your tank, such as algae. You might see small pieces of food or algae in their feces when Cardinal Tetras are new to the tank and still unfamiliar with most things. Even though you might not want it, Cardinal tetra’s will eat this food because they associate that type of food with survival.

Algae In The Tank

Cardinal tetras eat algae in their tanks. It is a common habit of these fish and won’t surprise most Cardinal tetras owners. These fish enjoy swimming under waterfalls or going into places where the current of a filter is vital because it resembles a river stream in nature.

Cardinal tetra will naturally feed upon bugs and insects found near moving water sources. If you have plants, rocks, driftwood, etc., Cardinal tetra might eat the algae that grow on them. These fish will also often swim up to the glass of a tank and scrape their faces against it, which is how they get algae off while feeding upon some in nature as well.

Is It Good To Let Cardinal Fish Eat Algae?

Cardinal tetras are freshwater fish belonging to the characin family. They do not usually eat algae as part of their diet, but they might take some from plants and rocks. There are both advantages and disadvantages of algae in Cardinal tetras. So, it is difficult to say whether it is good or bad.

Benefits Of Algae In Cardinal Tetras

Some of the benefits of algae-eating in Cardinal tetras are:

  • Cardinal tetras will clean up the tank when they eat algae.
  • Algae will fulfill the Cardinal tetras’ dietary needs.
  • Cardinal Tetras that eat algae tend to be healthier and more active as a result of their diet.
  • Some algae assist in the digestion process of Cardinal tetras.

Cons Of Eating Algae

Although algae seem to be an easy and good nutritional source for Cardinal tetras. All the algae are not beneficial to the health of these fish. However, some of the disadvantages of eating algae in Cardinal tetras are:

  • Cardinal Tetras can get ill and disease by eating the wrong type of algae.
  • In addition, some types of algae might be toxic to Cardinal tetras.
  • Lack of variety. Cardinal tetras require a nutritionally balanced diet that contains many different foods, not just algae.
  • Cardinal Tetras can die from eating too many algae as it may adversely affect their digestive system and liver.

How To Stop Cardinal Tetras From Eating Algae?

Cardinal Tetras eat algae naturally, and it is a common problem for owners. The good news is that there are several ways you can avoid this issue from happening!

The first step in stopping Cardinal tetras from eating algae is to make sure the tank they live in has enough food available. Cardinal tetras enjoy algae, but they also eat dried flakes and pellets. So when there is enough food available in the tank, they won’t go hunting for algae.

The next step in stopping Cardinal tetras from eating algae is ensuring that your tank’s water conditions are appropriate for these types of fish. They will get sick if they live in dirty water without proper filtration. If your tank’s water quality is poor, Cardinal tetras may start eating algae.

If both of these steps fail to solve your problem with Cardinal tetras eating algae, you may want to consider relocating the Cardinal tetras. Cardinal Tetras can feel stressed out in crowded tanks. Cardinal tetras living in groups may be happier than those who live alone in a small tank.

After trying all of these solutions, it is time to visit the pet store for professional help if you still have problems. Cardinal Tetras are susceptible fish, and it is important to do everything you can to keep them healthy.

What Is The Best Diet For Cardinal Tetras?

Cardinal tetras are very easy-going fish. They do not have any special food requirements and can eat any and everything. Moreover, these fish are omnivorous so, they need both plant and animal nutrients.

Plant-Based Food For Cardinal Tetras

The Cardinal tetra fish diet must include plant-based food for a longer and healthier life. Most Cardinal tetras in the aquarium eat any and everything that you give them. But they always prefer fresh vegetables over anything else. So for an entirely plant-based meal, you can feed them blanched lettuce leaves, spinach leaves, boiled zucchini slices, or algae wafers.

Animal Food For Cardinal Tetras

Cardinal tetra fish diet must also include animal food that comes from a healthy source. You can feed them bloodworms, brine shrimp, and tubifex worms every once in a while, but you have to be careful with the frequency of feeding these live foods. Cardinal tetra fish are not immune to diseases. They can suffer from deadly diseases like ich and velvet disease carried by live foods, especially brine shrimp and bloodworms.

Some FAQs

What Are The Types Of Algae Cardinal Tetras Eat?

There are three types of algae that Cardinal Tetras can feed on in the wild. They are cyanobacteria (blue-green algae), Ulva (sea lettuce), and various diatoms. Cardinal Tetras in the aquarium can feed on these types of algae if they are available to them. In captivity, Cardinal tetras might eat the algae that accumulate in the aquarium.

What Are The Types Of Algae Bad For Cardinal Tetras?

You should never give Cardinal tetra fish algae called Valonia. Cardinal tetras are not able to digest this type of algae. Their digestive tracts will become blocked due to the consumption of these algae. Some other harmful algae to Cardinal tetras are Caulerpa, Ulva (red algae), filamentous algae, and bristle-type algae.

What Can I Feed My Cardinal Fish Instead Of Algae?

You should look for high-quality flake food and supplement with frozen brine shrimp. Cardinal Tetras will eat algae in the tank, but they do not continually target it specifically. Some of the algae that are beneficial to Cardinal tetras are just by-products of their eating habits. If you see your fish nipping at some algae here and there is a good sign.

What If Cardinal Tetras Eat Too Many Algae?

In most cases, Cardinal tetra eating algae is a good thing and indicates that their tank conditions are right where they need to be. In some situations, though, excessive amounts of aquarium algae can become detrimental to the overall health of your Cardinal fish if not removed from time to time. So Cardinal tetra eating algae is a good sign. But if they are targeting specific pieces, you should move your fish to prevent them from eating it all up.


Cardinal tetra fish enjoy a plant-based diet, and their consumption of algae is not necessary for survival. However, depending on the tank you have, it may be possible that your Cardinal Tetra will eat some green algae or leftover food from other fish in its habitat.

If you want to feed your Cardinal Tetra only plants, then provide them with vegetation high in fiber, such as dried leaves, or add a plant fertilizer into their water to get nutrients from it. But still, it isn’t a good idea to do that.

For the proper growth and well-being of your fish, they need both plants and protein. Therefore, a good diet will consist of a variety of both plant-based and meat-based food, so your Cardinal Tetra can lead a long, happy life in its natural habitat while eating healthy at the same time.

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