Constipation In Cardinal Tetras |Causes, Symptoms & Treatment

Feeding Cardinal tetras has always been a source of anxiety for many aquarists, and the cardinal tetra is no exception. While it may be tempting to feed your fish as much as they’ll eat, overfeeding tropical fish can cause severe constipation that results in death. Generally, constipation is one of the leading causes of death in freshwater fishes like Cardinal tetras.

Constipation in Cardinal tetras is when the fish has a problem passing feces, causing hardening of stool. Usually, smaller fishes like cardinal tetras suffer from this condition when you overfeed them with fatty or high-protein foods to the point that they exceed their digestive capacity.

The most common cause of constipation is parasites. So, the symptoms will vary depending on the type of parasite affecting your fish.

Today, we discuss the causes, symptoms, and treatment of Constipation in Cardinal Tetras and how to prevent it from happening.

Constipation In Cardinal Tetras

Being omnivores, Cardinal tetras can eat many different types of food, including both plant and animal matter. Moreover, they are likely to feed on the foods that are most readily available in their environment. So, constipation appears to be a pervasive issue among Cardinal tetras that live in aquariums.

Constipation can cause blockages that prevent the fish from passing feces, leading to malnutrition and eventually the death of your pet. However, constipation can have many different causes, so you will need to figure out the exact reason behind it.

What Are The Causes Of Constipation In Cardinal Tetras?

There are several potential causes for constipation and bloating in cardinal tetras. The most common reasons are:


Parasites often affect Cardinal tetras, particularly Nematodes (roundworms). Constipation is one of the most common symptoms of roundworm infection.

External parasites like Ichthyophthirius multifiliis (commonly known as “Ick”) also affect cardinal tetras and lead to bloating and constipation. In this condition, the cardinal tetra’s body turns white, becoming bloated due to parasites in its digestive tract.

Lack Of Fibers

Most owners believe that the lack of fibers is one of the significant causes of constipation and bloating. So, you should provide Cardinal tetras with a diet that contains at least some amount of plant material. The fish need to digest any food they eat, and fiber helps them do this while also helping move their digestive system normally.


Cardinal tetras are relatively small fish. Therefore their digestive system is not able to process food as quickly as more prominent species. As a result, constipation can occur if they overeat at once or do not get enough water flowing through the tank, making it harder to digest what they have eaten.

Switching Foods

Switching from one food type to another can cause constipation. Therefore, cardinal tetras need to eat a varied diet. But it would be best to introduce your fish to these food gradually and not all at once.


Some medications can cause constipation in fish. Antibiotics, antidepressants, and even some water treatments can lead to the condition. Constipation may be one side-effect, or it might not become apparent until after a few days.

Swim Bladder Disease

Swim bladder disease is a common cause of constipation in fish. If the swim bladder becomes diseased, it can prevent cardinal tetras from swimming properly, and bloating may occur as a result.

Fluctuation In Water Temperature

The water temperature should be within the recommended range for cardinal tetras, between 22 and 28 degrees Celsius. If it falls outside of this range, then your fish may not digest their food correctly and will suffer from constipation as a result.

Insufficient Food Intake

Feed your cardinal tetras twice every day. If you are not feeding them enough, they may be unable to pass any food that is still in their digestive tract.

Poor Water Quality

Make sure the water quality of the tank meets all standards for maintaining healthy fish life. It should have a pH level between six and eight, low to moderate ammonia levels, and nitrite levels close to zero. It should also have a steady temperature between seventy-two and eighty degrees Fahrenheit.


Overfeeding cardinal tetras can cause them to become constipated. Constipation is also more common in fish that contains dried foods in their diet. Again, it is because dried foods take longer for the digestive system to process than other types of food.

What Are The Symptoms Of Constipation In Cardinal Tetras?

Several symptoms can indicate cardinals tetra fish are suffering from constipation, including:

Bloating In The Middle Section

The cardinal tetra’s belly will appear inflated. In addition, there may be visible bulging along Cardinal tetras’ midsection. In addition, the abdomen may hang low and appear sagging, especially behind the gills.

They May Stop Eating Or Appear Disinterested In Food

If your cardinal tetra fish suffer from constipation, they will often stop eating or show no interest in the food you put into their tank. They can also lose weight over time as they lose the appetite to feed.

Decreased Activity

A cardinal tetra fish suffering from constipation will often become less active and more sedentary than usual, spending lengthy periods resting on plants or at the bottom of their tank. It can cause them to stop interacting with other members of their school and appear depressed.

Discolored Skin Or Fins (Reddening)

If your cardinal tetra fish suffer from constipation, they may develop red patches on the skin around their face and pectoral fins. They can also become discolored under certain conditions, such as when breeding or in brackish water environments.

Swimming In Circles And Bumping

When the cause of constipation is an issue related to the swim bladder, your cardinal tetra fish will often swim in circles or bump into objects. They may even appear upside down at the bottom of their tank, unable to turn themselves around.

Swelling On The Head And Gills (Pop Eye)

Cardinal tetras suffering from constipation can develop swelling on their head and also around the gills. The medical term for this is “Popeye” and will cause the cardinal’s eyes to bulge outwards, giving them a peculiar appearance. It can often be the first sign you’ll notice that something is wrong with your fish.

How To Treat Constipation In Cardinal Tetras?

Constipation In Cardinal tetras can last from a few days to several weeks. So it is important not to feel frustrated if your fish does not recover quickly. It will eventually go away without any intervention.

But if you want faster results, use the following ways to treat constipation In Cardinal tetras,

  • Change the water in your tank. You can do this by removing a third of the old water and replacing it with fresh tap or aquarium water.
  • Use an antibiotic medication to treat any bacterial infections that may be present. These medications are available at most pet stores and online.
  • Administering an enema will also help constipation in Cardinal tetras. But remember, only skilled professionals must do it at pet stores or veterinarian offices.
  • You can even treat constipation in Cardinal tetras by adding Epsom salt to your fish tank. For every five gallons of water, add one tablespoon of the salt and stir it well. But remember that this is only a temporary solution.

However, if constipation in cardinal tetras persists for more than two weeks, then it’s time to visit the vet, as they might prescribe some other medications that are safe for your fish.

How To Prevent Constipation In Cardinal Tetras?

Cardinal tetras are usually hardy fish that can survive in water conditions most tropical freshwater fish cannot. However, this does not mean they never get sick or suffer from diseases like other aquarium pets.

Constipation is one of the more common problems with cardinal tetras. So, it is better to prevent this disease rather than search for treatment afterward. Some of the preventive ways of constipation in Cardinal tetras are:

Maintain A Healthy Water Temperature In The Aquarium

Constipation is most common when cardinal tetras live at room temperatures of 60 degrees Fahrenheit and below for prolonged periods. When it gets colder than this, their digestive system slows down, leading to constipation. An excellent way to prevent such issues is by maintaining proper water temperature conditions: 76 to 82 degrees Fahrenheit.

Maintain Optimal Water Conditions

Constipation also results when water conditions are not ideal for cardinal tetras. Or if there is a sudden change in the quality of water. For a healthy environment, the pH level should be between 4 to 6, hardness levels at 2 to 10 dGH, and carbonate hardness from 1 to 2 degrees. Any change in these parameters can affect your Cardinal tetras’ well-being.

Feed The Right Amount Of Food In Small Bites

Cardinal tetras are small fish. So, you must feed them with the right food at least three times a day. You can even exceed four if there is an increase in cardinal tetra fish in one aquarium.

When there are just a few cardinal tetras in the aquarium, it is better to feed them small amounts of food at regular intervals rather than one big meal. An excellent way to do this is by using a high-quality automatic fish feeder that you can program in advance.

Feed Cellular Foods In Combination With Other Types Of Food

An excellent way to prevent constipation in the cardinal tetras is by feeding them cellular foods. It includes zucchini and cucumber slices as well as algae wafers.

Cellular foods are rich in fiber. So, these food are essential for the digestive system of cardinal tetras to function normally.

Use The Right Type Of Food

Cardinal tetra fish require a high-quality flake or pellet food designed especially for small tropical freshwater fishes like them. These types of foods provide the fish with all the nutrients they need.

Feed Them At The Right Time

The cardinal tetras should be fed at least three times a day, preferably around the same time each morning and evening. However, aquarists do not recommend underfeeding these fish. Since they will eat whatever food comes their way quickly, insufficient nutrients lead them to munch on tank wastes and plants. As a result, it can lead to constipation in Cardinal tetras.

Visit The Vet

As mentioned earlier, if none of those ways work to prevent constipation in cardinal tetras, it is essential to consult a veterinarian as soon as possible. A good vet will first ask about the condition of your aquarium and then take a look at how well you have been feeding them. They may even recommend a change of diet.

What Are The Foods That Causes Constipation In Cardinal Tetras?

Constipation in Cardinal tetras might occur due to many different factors. However, the primary factor is the type of food you are feeding them. You should never give certain foods to cardinal tetras because it will result in constipation later on.

Such foods are:

  • High protein foods like krill, clams, and shrimp.
  • Too much fat or oil content in the fish food like butter, cream cheese, and some oils.
  • High fiber foods like beans, peas, and peanuts.
  • Sweets and fatty foods like sugars, chocolate, and donuts.
  • Any type of junk food like potato chips and corn chips.
  • Raw vegetables or sprouts with bacteria in them.
  • Any bread.
  • Cereal and oatmeal that are high in fiber content
  • Seeds like sunflower seeds, pumpkin seeds, or flaxseed which contain too much fat content

What Is The Best Diet For Cardinal Tetras?

The best diet for cardinal tetras is one with a high amount of fiber and the correct nutritional balance.

Cardinal tetras should be fed foods such as:

  • Brine shrimp or bloodworms (live, frozen, or freeze-dried)
  • Both live or commercially prepared plant matter, including algae wafers
  • Dried flakes and granules
  • Vegetable matter, such as zucchini or spinach (many fish love to eat fresh vegetables)

Cardinal tetras may also eat live blackworms. A varied diet is best for all fish so try feeding brine shrimp one day then bloodworms the next. Varying their diet will not only stop the cardinal tetras from feeling bored with what they are eating. But it can also increase their lifespan.


Lastly, it is essential to keep in mind that the best way of preventing constipation and impaction, or any other disease for this matter, is by providing your fish with a proper environment.

Some of the best home remedies you may use to cure constipation, and other problems include:

  • Feed your fish, lettuce, and other vegetables.
  • Using Epsom salt
  • Constantly check your aquarium to ensure that it is free from any bacterial infections like Aeromonas or Pseudomonas.
  • Monitoring the water parameters
  • Have good filtration and aeration systems in place because they prevent any buildups inside the tank.

Hopefully, all these will help you cure the problem.

Good luck!

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