Cardinal Tetra Diseases and Treatments: Caring for a Fish with a Chronic Disease

Cardinal tetras are beautiful fish with vibrant colors and personalities. But, unfortunately, Cardinal Tetras are susceptible to a few different diseases and disorders that can quickly turn their vibrant colors into dark shades of gray, or the fish may become lethargic or have difficulty swimming correctly. So, it is essential to get effective treatment of Cardinal tetra diseases in time.

Some of the common diseases of Cardinal tetras are swim bladder disease, fin rot, ich, velvet, and black spot disease. An ideal tank with proper water parameters, enough space, and a well-balanced diet can prevent Cardinal tetras diseases. But in some severe cases, you need to consult with your fish veterinarian.

In this post, we will discuss the different diseases of Cardinal tetras with some treatments and ways to prevent them.

Cardinal Tetra Diseases And Treatments

Cardinal tetras are hardy fish that are usually healthy. But they are also susceptible to many diseases. Their diseases are often chronic because they can recur easily due to their environment and tank mates.

Some Cardinal tetras diseases resolve efficiently without much treatment, whereas some diseases can be deadly. So it is important to identify the diseases at the first time of appearance before further damage occurs.

Some of the most common Cardinal tetras diseases include;

Fungal Infections

Cardinal tetras are prone to fungal attacks. The fungus damages the fins and skin of Cardinal Tetra fishes, often causing them to lose their coloration.

The fungus enters into the tank through new fish, plants, or even decor items like rocks, etc. So it’s important to quarantine any newly added Cardinal tetras for at least two weeks before transferring them into your Cardinal Tetra tank.


Some of the symptoms of fungal infection in Cardinal tetras are;

  • Loss of coloration
  • Fins and tail rot
  • Skin ulcerations.


If you want to treat fungus, it is important to make sure that the water quality in the Cardinal tetra fish tank is excellent since fungal infection occurs more often under poor environmental conditions. So ensure good filtration and change the water weekly.

Ichthyophthirius (Ick)

Ick is also common as a “white spot disease” because it causes small white spots on Cardinal Tetra’s body.

The parasite causing Ick can be present in new fish or plants you introduce into the tank. So quarantine these Cardinal tetras for at least two weeks before transferring them to your tank.


Some of the common symptoms of Ick in Cardinal tetras are;

  • Loss of coloration
  • Scratching and flashing against tank ornaments
  • Clamped fins with rapid gill movement.


Since Ick is highly contagious, so, most aquarists recommend treating the Cardinal tetras tank with a commercially available anti-Ick medicine as soon as possible.


Dropsy is a disease in Cardinal Tetras in which a Cardinal tetra fish’s scales protrude out, causing the body to swell. This disease occurs due to bacterial infections and poor water conditions. So make sure you maintain good filtration and change 20% of tank water weekly for healthy fish.


Cardinal tetras symptoms of dropsy include;

  • Bloated stomach
  • Sunken belly.
  • Swollen eyesocket or scales sticking out from the Cardinal Tetra fish body.


Cardinal tetras diseases treatment for dropsy often includes adding one tablespoon of salt per gallon of Cardinal Tetra tank water and increasing the temperature to about 82°F with constant aeration running in your Cardinal tetra fish tank. This will help reduce fluid build-up, but remember that this treatment is only temporary.

Fin Rot

Sometimes nitrates present in the tank can cause damage that leads to loss of tissue from the fins, tail, or even body of Cardinal Tetras. Thus, fin rot occurs in an environment with poor water conditions, ensuring good filtration and weekly Cardinal Tetras Tank Water changes of 20%.


Cardinal tetra symptoms of fin rot include;

  • Ragged fins or tail.
  • Gill damage due to bacterial infection
  • Ulcerations on the body of Cardinal tetra fish
  • Loss of coloration on the Cardinal Tetra fins
  • Redness or damage to Cardinal tetra’s tail.


Treatment for Fin Rot includes adding salt and raising the temperature of your tank up a few degrees. Besides this, you can also use some medicines as per the recommendation of a veterinarian. However, it is best to start the treatment only after consulting the Vet.

Swim Bladder Disorder

Cardinal tetra fish suffering from swim bladder disorder cannot control their buoyancy and they start to sink. So this disease makes it hard for them to get food or even breathe in water. So the fish suffering from this disease cannot swim efficiently and needs immediate help.


Cardinal tetras symptoms of swim bladder disorder include;

  • Restlessness and reduced activity level
  • Floating near the upper Cardinal Tetra tank water line


There is no specific treatment for swim bladder disorders. But you can improve the water conditions by regularly cleaning the tank, changing the water weekly, and using filters, air pumps, and airstones. Sometimes the Vet also recommends surgery of Cardinal Tetra fish swim bladder.

Gill Flukes

Gill flukes occur in the gills of Cardinal tetras and many other tropical freshwater fishes. Usually, this is a disease that occurs due to infections of parasites. The gills of fish acts as a host for the fluke and provides it will the nutrition to grow and multiply. This makes the diseases even serious.


  • Cardinal tetras symptoms of Gill Flukes include;
  • Flashing, rubbing on the bottom or sides Cardinal Tetra tank
  • Rapid gill movement Cardinal Tetra.
  • Lethargy Cardinal Tetras Diseases Treatment.


Some medications can treat diseases caused by parasitic flatworms. But you need to consult the Vet before using any drugs on Cardinal tetra. Also, remember that if you fail to follow the proper guidelines for Cardinal tetra diseases, these medications can be harmful.

White Spot Disease

Cardinal tetras might also suffer from white spot disease due to infection caused by a parasitic protozoan. This disease is more common in Cardinal Tetra fish during spring and summer.


  • Cardinal tetras symptoms of white spot disease include;
  • Fish scales sticking out Cardinal Tetr.
  • Scraping movements Cardinal Tetra tank.
  • Fish disorder leading
  • Lethargy
  • Reduced appetite


You can treat White spot disease with either Formalin or Malachite Green. But it is crucial to remember that while using Cardinal tetras medications, you should not overcrowd the tank and then increase the dosage of medication accordingly. Also, keep in mind that some medications can be harmful to Cardinal tetra, so you should first consult your Vet.

How To Keep Cardinal Tetra Diseases Free? Prevention Of Diseases

Cardinal tetra is a prevalent fish in the aquarium hobby. They are native to South America and come from blackwater rivers. Unfortunately, these diseases are prone to various types of health issues.

Some of the diseases occur naturally, while some result due to the lack of care. However, there are few ways to prevent the diseases of Cardinal tetras and ensure their health. Such as:

Keep Cardinal Tetras In Clean Water

One of the most important things to care for a fish is clean water. It provides oxygen and removes waste from their body, which results in better health conditions. Moreover, it will prevent diseases such as fin rot, bloating disease, etc. Apart from that, dirty or cloudy water can lead to bacterial infections on the fins and gills of Cardinal Tetra.

Keep The Water Temperature Constant

It is also important to keep the temperature of water constant for the healthy growth of Cardinal Tetras. They are tropical fish and prefer a temperature between 70-80 degree Fahrenheit in the aquariums.

It will result in a proper digestion process that prevents bloating diseases, among other common problems, while keeping the water at lower or higher temperatures.

Feed Cardinal Tetras A Balanced Diet

A balanced diet is essential for the healthy growth of fish. It will result in good health conditions and reduce the chances of diseases to a significant extent. There are various types of foods available which provide different nutrients required by cardinal tetra for better growth.

It is important to feed them a variety of foods in small quantities instead of over-feeding them. Overfeeding will result in bloating diseases and other digestion-related problems. So, it would be best if you avoided this as much as possible.

Keep These Things In Mind

You should keep in mind a few more things while keeping Cardinal Tetras fish in an aquarium.

Most of the diseases in cardinal tetra occur due to stress. So, it is important to keep them away from different types of stress-inducing factors, such as overfeeding, keeping dirty water, etc., which can result in various health issues.

They prefer a blackwater environment when kept with other fishes. So, you should monitor the water condition regularly when you add more fish to the tank.

It is essential to consider these things for the better health of Cardinal Tetras fish and enjoy their beautiful look throughout their lifetime.


Summing up, Cardinal tetra diseases are pretty common. If you want to make sure your fish stays healthy, provide it with a good home and feed it well. However, if you find that your cardinal tetras have any of these diseases or illnesses, the advice above should help you take care of them much better than before.

Hopefully, this post was successful in explaining how to take care of your tetras. If you have any questions, feel free to ask in the comments section below!

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