Cardinal Tetras

The Cardinal Tetra (Paracheirodon axelrodi) is a species of tropical freshwater fish native to the Orinoco and Amazon River basins in South America. They are one of the most popular aquarium fish due to their vibrant colors and non-aggressive personality. 

Cardinal Tetras are best kept in groups of at least six individuals. Because they’re schooling fish they’ll be more active and colorful when kept in larger numbers. They should be kept in an aquarium with plenty of plants and hiding places, because they prefer dimly lit tanks.

They prefer to live in schools, so it’s important to keep them with other Cardinal Tetras or similar species. They do best in an aquarium with plenty of hiding places and plants that mimic their natural home in river basins.

Cardinal Tetras are active swimmers and enjoy exploring their environment. They are also very social and will interact with other fish in the tank.

Cardinal Tetras are relatively easy to care for and don’t require a lot of maintenance. They can be a problem to care for if your aquarium conditions fluctuate. If you have problems maintaining stable conditions in your aquarium these might be a better fish for your family later.

Overall, Cardinal Tetras make great family pets for new fish owners. They are easy to care for, peaceful, and colorful. With proper care, they can live up to five years. If you’re looking for a unique addition to your aquarium, consider adding some Cardinal Tetras.

Cardinal Tetra Information

  • Average Length: 1.5 – 2 inches
  • Scale Colors: Blue, red, silver
  • Attention Needs: Low
  • Good Pet: Yes!
  • Safe with Children: Yes
  • Tolerance to Heat and Cold: Yes
  • Good with Other fish : yes as long as they’re a peaceful species
  • Good with Other Cardinal Tetras: They enjoy living in groups
  • Suitable to live in an Apartment: Yes
  • Good for Less Experienced Pet Owners: Yes
  • Weight Gain: No
  • Health Concerns: White Spot Disease, fin rot, velvet, dropsy
  • Allergies: None
  • Average Life Span: about 5 years

Physical Appearance Cardinal Tetra Fish

The Cardinal Tetra has an elongated, translucent body with a bright red stripe running along their sides, and a blue line running above the red line. Their fins are transparent and they have a white or silver belly. The males tend to be more colorful than the females, with brighter red stripes and longer fins. They’re a small fish, growing between 1 and 1.5 inches long.

Their bright colors are believed to help them locate each other in black waters which they love (black water is an environment where the water is murky and the visibility is reduced). It’s also not uncommon to see your Tetras colors looking faded especially when they’re sleeping or feeling sick.

Temperament of Cardinal Tetras

Cardinal Tetras are peaceful fish that should be kept with other peaceful species. They are schooling fish and should be kept in groups of at least six individuals, because they will be more active and colorful when kept in larger numbers. If kept in smaller groups they can become stressed or bullied by more aggressive species. To keep them from being bullied it’s important to choose their tankmates carefully. Cardinal Tetras are not known to be territorial and shouldn’t bother other fish or plants in their tank.

Cardinal Tetras are a popular and attractive freshwater fish that makes a great addition to any family aquarium. They are relatively hardy and easy to care for, but they’re sensitive to water parameter changes. Regular water changes are essential for keeping them healthy.

Tank Conditions

Cardinal Tetras like acidic water in their aquarium. They prefer a pH level between 4.6 – 6.0, but they should be OK with a pH up to 7. Their ideal temperature range is between 73.5° – 80.5°F. It’s also important that they have plenty of hiding places and plants in their aquarium. 

Cardinal Tetras are sensitive to light, and this is why it’s important to give them plenty of hiding places and shade. They shouldn’t be exposed to direct sunlight or bright lighting, because this can cause stress and illness. They also shouldn’t be kept in tanks with strong currents or high levels of nitrates, because this can also cause stress and illness.

Tank Maintenance

In order to keep your Cardinal Tetras healthy and happy, it’s important to do regular water changes and use an aquarium filter. Their tank should be kept clean by removing any uneaten food or debris. It’s also important to check the water parameters regularly and make sure they are within the recommended range for Cardinal Tetras.

Cardinal Tetras don’t release a lot of bio waste like Goldfish. A complicated or sophisticated filtration system isn’t usually needed if they are your only fish. A simple sponge filtration won’t have a problem maintaining a healthy habitat for your Cardinal Tetras.

Best Tank Mates for Cardinal Tetras

They like to stay in a large pack and will rarely move around alone in their tank. The Cardinal Tetra is small, and because they’re so small a lot can fit comfortably into most aquariums. 

Cardinal Tetras are peaceful fish and can be kept with other peaceful species such as:

They shouldn’t be kept with aggressive or large fish, because larger fish can bully or eat them.

Health Issues

Cardinal Tetras are sensitive to medications, so it is important to use caution when treating the tank for any illnesses. It’s best to use a quarantine tank when medicating your fish. A quarantine tank will help prevent any adverse reactions to the treatment. They shouldn’t be exposed to sudden changes in temperature or pH levels, because this can cause stress and illness.

Some of the more common illnesses Cardinal Tetras can have are:

Swim Bladder Disease

Swim Bladder Disease is a common health issue in Cardinal Tetras. It’s caused by an imbalance of gasses in their swim bladder, which affects the fish’s ability to stay afloat and control its buoyancy. Symptoms include difficulty swimming, floating upside down or sideways, and a bloated abdomen. If left untreated, it can lead to death. Treatment includes changing the water parameters, adding aquarium salt, and providing a high-quality diet.

The best way to prevent swim bladder disease in Cardinal Tetras is to maintain good water quality and provide a high-quality diet. Regular water changes are important, as well as avoiding overfeeding. It’s also important to make sure that the tank has plenty of oxygen and that the temperature is not too high or too low.

Fin Rot

Fin rot is a common disease that can affect Cardinal Tetras. It’s caused by bacteria and can be seen on your fish by the deterioration of their fins. Over time their fins can become frayed or discolored. In severe cases, their fins may even fall off completely. Fin rot can be caused by poor water quality, overcrowding in the tank, or injury from other fish. 

To prevent fin rot, it’s important to keep the tank clean and maintain good water quality. It’s also important to avoid overcrowding and ensure that any aggressive fish are kept separate from your Cardinal Tetras. If fin rot does occur, it can be treated with antibiotics or other medications.

If fin rot does occur, it can be treated with antibiotics or other medications. It is important to follow the instructions on the medication carefully and to monitor your fish closely during treatment.

White Spot Disease

With white spot disease, your fish will have white spots on their body. Ich is highly contagious and can quickly spread to other fish in your tank. If your Cardinal Tetra is infected with Ich, make sure you quarantine them immediately. The disease can be cured by raising the temperature of the tank. There are also commercial Ich solutions available that can help to cure your fish. Consult a vet if the problem persists.

Black Spot Disease

Black spot disease, also known as black spot syndrome, is a common health issue among Cardinal Tetras. It is caused by a parasite called Ichthyophthirius multifiliis, which attaches itself to the fish’s skin and gills. Symptoms of black spot disease include white spots on the body and fins of the fish, along with dark patches or spots that can appear on their head, body, and fins. 

Your fish may also show signs of distress such as scratching against objects in the tank, loss of appetite, and lethargy. Treatment for black spot disease isn’t hard. The easiest way is to increase the water temperature to 80.5°F and add aquarium salt to the tank at a rate of 1 tablespoon per 5 gallons of water. It’s also important to remove any carbon from your filters and to perform regular water changes. Carbon in the filters can make the medication worthless. In severe cases, a medication such as copper sulfate may be necessary to eradicate the parasite.


Velvet disease, also known as gold dust disease, is a common ailment among Cardinal Tetras. It is caused by the single-celled parasite Oodinium ocellatum, which attaches itself to the fish’s skin and gills. The parasite causes the fish to develop a golden-brown or yellowish coating on their body, giving it a velvety appearance. This disease can be fatal if left untreated. It’s important to recognize the symptoms and take action quickly. 

Symptoms include lethargy, loss of appetite, clamped fins, and rapid breathing. If you suspect your Cardinal Tetra has velvet disease, it’s important to quarantine them from other fish and treat the tank with a medication specifically designed for this type of parasite.


Dropsy is a condition that affects Cardinal Tetras, as well as other fish species. It’s caused by a bacterial infection and is known for swelling of a fish’s abdomen. Other symptoms can be bloating, lethargy, loss of appetite, and difficulty swimming. The disease is often fatal if left untreated. 

Treatment for dropsy includes antibiotics to fight the infection and water changes to reduce stress on the fish. It’s important to quarantine any affected fish and treat them as soon as possible to prevent the spread of the disease.

The Attention Needs of Cardinal Tetras

Cardinal Tetras are peaceful fish that don’t need a lot of attention. However, it’s important to check the water parameters regularly and make sure they are within the recommended range for Cardinal Tetras. It’s important to give them plenty of hiding places and plants, as well as regular water changes and an aquarium filter.

Feeding Cardinal Tetras

Cardinal Tetras should be fed a diet of flakes, pellets, frozen, and live foods such as brine shrimp. It’s important to feed them small amounts several times a day, and this will help reduce overfeeding and water pollution. It’s important to remove any uneaten food or debris in order to keep the tank clean.

Related Questions:

How Many Cardinal Tetras can Live in a 20 Gallon Tank?

Depending on the stability of your aquarium’s water, and the quality of your water filters we don’t recommend having more than 15. If your aquarium has swings in its water parameters then we suggest not going above 10. If you have other fish being kept with your Cardinal Tetras then obviously we’ll recommend even less.

Neon Tetra vs Cardinal Tetra: Which Should I Get?

Both are great fish. They look very similar and enjoy many of the same water conditions, and they’ll even school together. But if for some reason you had to choose just one we suggest the Neon Tetra because they handle water condition changes slightly better than the Cardinal Tetras do. Both make great starter fish!

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