Cardinal Tetra: Care, Size, Breeding, Diet & More

Cardinal Tetra (Paracheirodon axelrodi) is a peaceful, schooling fish that makes an excellent addition to any freshwater aquarium. They are known for their beautiful bright red and blue coloration, which can be quite striking against a black background or when the light catches them just right.

Cardinal Tetras are very active and love to swim in groups, so it’s best to keep a group of them together for the best viewing experience. They are also quite hardy, so they can tolerate a wide range of water conditions as long as regular water changes are done. 

With proper care and maintenance, these tetras will bring life and color to your aquarium for many years! 

In this article, you will be provided with the necessary instructions on how to properly take care of Cardinal Tetras, as well as other relevant information.

Species Profile & Overview

Cardinal Tetra fish are native to the rivers and streams of South America, primarily in the upper Orinoco and Negro Rivers Basins. They prefer to live in slow-moving waters with a neutral pH, low levels of pollutants, and plenty of vegetation. 

The cardinal tetra has several unique features that help it survive in these waters, such as its long dorsal fin which helps them navigate swiftly through currents. Its bright colors also help it blend in with its environment, making it harder for predators to spot them. 

Cardinal tetras are peaceful fish that get along well with other non-aggressive tankmates. They tend to be fairly timid, so they should not be kept with overly aggressive species or fish that are much larger than them. 

Cardinal tetras enjoy being in shoals of at least 6 individuals, which allows them to feel secure and comfortable. They also prefer to swim in the middle level of the aquarium, but will occasionally move up toward the surface and bottom when seeking food.

These fish are incredibly beautiful to look at, with their bright red and blue colors. They also have a peaceful temperament, making them an ideal addition to a community tank. 

They are easy to care for but are not beginner fish. This is because they need a very stable tank with minimum parameter fluctuations. 


School of Cardinal Tetras
School of Cardinal Tetras

The Cardinal Tetra is one of the most gorgeous fish in the aquarium hobby. They look very similar to Neon Tetra except that Cardinal Tetras grow larger and have their belly fully covered with red colors. 

Their body is divided horizontally into a full blue upper body and full red lower body. Not only do they have an eye-catching coloration, but they also feature iridescent scales that shimmer and sparkle when the light hits them just right. They are truly a sight to behold!

Like Neon Tetras, Cardinals have long, slender, and compressed bodies with rounded bellies. Their head is pointed and their mouth is slightly upturned. They have a long and pointed dorsal fin that is placed right above the anal fin. 

However, their anal fin is what gives them a unique look. They have a forked caudal fin that gives them an additional degree of maneuverability in the water. 

Despite their small size, they are relatively hardy, easy to care for, and peaceful. All in all, Cardinal Tetras is an excellent choice for any aquarium!

Adult Size

Cardinal tetras are small fish that typically reach an adult size of 1.5 – 2 inches (3.8-5 cm). Although males and females of the same species tend to be similar in size, there can be slight variations between individuals.

Cardinal Tetra fish make great pets because of their small size. So they can fit comfortably in medium size aquariums. This makes them ideal for people who want a school of fish but do not have a lot of space for a larger aquarium.


The average lifespan of a cardinal tetra is around 5 years, though with proper care they can live longer in captivity. They can only live a long life if you provide them with the proper care they need.

Genetics can play an important role in lowering the lifespan of Cardinal Tetra fish. Inbreeding and a lack of genetic diversity can lead to shortened lifespans. Stress, such as overcrowding or changes in water conditions, can also reduce the lifespan of these fish.

Finally, diseases such as bacterial infections and parasites can greatly reduce the lifespan of Cardinal Tetra fish if they are not treated quickly and properly. 

Behavior & Temperament

Cardinal tetras are peaceful schooling fish that will typically get along well with other peaceful fish of similar size. They are very active swimmers, so they will do best in a tank with plenty of open swimming space. 

Cardinal tetras are a great choice for community tanks. They are peaceful, non-aggressive, and can live in both small and large aquariums. When kept in small aquariums or when the tank is overcrowded, they may become stressed and develop diseases. To avoid this, it is important to keep their tank clean, not overcrowd them, and provide plenty of hiding places.

They are schooling fish, meaning they prefer to live in groups with other Cardinal Tetras or other compatible species. In the wild, these fish form large schools that can number into the hundreds or even thousands.

In captivity, it is best to keep them in groups of six or more as this allows them to display their natural behavior. When kept in smaller numbers, they may become shy and timid. To see their true schooling behaviors it’s best to keep them in large numbers and in a large aquarium.

These fish are known for their tight schooling behaviors that can entertain their owners for hours. They are also larger than neon tetras which makes it easier to spot them in a tank. 

Cardinal Tetra Care

Cardinal Tetras are easy to care for when tank setup is done right. They thrive best in heavily planted tanks with plenty of places for them to hide. Providing plenty of covers and hiding spots, as well as regular water changes, will go a long way toward keeping your Cardinals healthy and colorful.

Cardinals are extremely adaptable species that are able to adjust to different environments. This makes them a great choice for many aquariums, as they can thrive in a variety of conditions. 

However, it is important to make sure that the parameters of the aquarium match what they would experience in the wild. This includes water temperature, pH level, hardness, and other factors. With this in mind, cardinal tetra fish can easily adjust to their new environment and become very active and lively inhabitants of any aquarium.

In the next few sections, we will explain how to properly create an ideal living environment for your cardinal tetras. So keep reading for all the essential Cardinal Tetra care requirements!

Tank Size

Cardinal tetras are schooling species and they can grow to about 2 inches in length. This means the minimum tank size for them should be 30 gallons or more. Although smaller groups of 3 – 5 can live in a 20 gallon aquarium as well.

Cardinal Tetras are schooling fish, so they should be kept in groups of at least six and preferably more. They also need plenty of swimming space and should not be overcrowded, as this will lead to stress and disease. 

What To Put In A Cardinal Tetra Tank

Aquascaping for Cardinal Tetra fish is all about creating a peaceful, natural environment. The best way to do this is to create a planted aquascape with plenty of hiding places. 

Plants will provide the tetras with plenty of hiding spots and also look great when combined with other decorations such as driftwood, rocks, and caves. Be sure to leave plenty of open swimming space, as these fish love to zip around their tank! 

Using natural decorations like rocks, driftwood, and live plants in an aquarium has many benefits. These natural decorations create a more realistic environment for your fish and other aquatic life. 

They also add visual interest to the tank, making it look more beautiful and natural. The rocks can provide surfaces for beneficial bacteria to grow on, while the driftwood can provide shelter for fish to hide in. 

The wood also helps to stabilize the pH of the water, and can even provide food sources for some types of fish. Natural decorations also help reduce stress levels in fish, as they feel more secure when they have places to hide or explore. 

The substrate is an important part of any aquarium, including a Cardinal Tetra aquarium. It helps to provide a natural environment for the fish and can also be used to create interesting visual effects. 

The substrate will also play an important role in helping to maintain water quality by providing a place for beneficial bacteria to colonize, which helps to break down toxins and waste in the water. This is an important thing to keep in mind as cardinal tetras need super clean waters.

Once the fish waste is broken down by the beneficial bacteria, your live plants can absorb them and keep the tank clean. You can add almost any type of aquarium plants you want but our top pics are hardy species like Moneywort, Rotala Indica, Buce Plants, and Rotala Rotundifolia

Not only can live plants bring life and color to the tank, but they can also provide numerous benefits for the health of the fish. Live plants create a more balanced and natural environment for the fish, providing hiding places and areas of protection from predators. 

Having live plants in an aquarium also increases oxygen levels, helps to absorb toxins such as nitrates and ammonia, and can act as a natural filter. All of these benefits make having live plants in an aquarium essential for creating a balanced and healthy environment for Cardinal Tetra fish.

Additionally, make sure to provide adequate circulation throughout the tank and replace 10 – 20% of the tank’s water weekly with fresh dechlorinated water. This will give you cardinal tetras a healthy living space inside your home.

School of Cardinal Tetras
School of Cardinal Tetras

Light Requirements

Lighting is an important factor to consider when setting up a Cardinal Tetra tank. These fish are most beautiful in bright light with a lot of contrast, such as white lights. This will bring out their bright red and blue colors. Keeping the lights on for 8-10 hours each day will help your Cardinal Tetras look their best while letting the plants grow naturally.

The best type of light for an aquarium is LED lighting, as it is energy efficient and lasts longer than other types of lighting. When buying a light, it’s important to consider the size of the tank, the plants you want to grow, and the other fish you have.

It’s also important to buy a light with adjustable settings so that you can adjust the light intensity depending on your needs. This way you can get the right amount of light for your aquarium without wasting energy or money.

Water Conditions & Parameters

Cardinal tetras are very adaptable and hardy fish, but it is important to match the water parameters of the tank to their natural habitat to ensure that they remain healthy. Cardinal tetras prefer slightly acidic water with a pH between 5.0 and 7.0, and a temperature ranging from 74 – 82°F (23 – 28°C). 

The flow should be slow or moderate as these fish prefer to live in slow-moving waters. In their natural habitat, they live in still or very slow-moving bodies of water where light can reach the bottom and plants can grow.

This means they need soft, clean water with plenty of oxygen, so it is important to maintain good water quality and regular partial water changes. 

Changing the water in an aquarium is an important part of keeping it healthy. This should be done once a week, and no more than 25% of the water should be changed at one time. This helps to keep the levels of ammonia, nitrite, and nitrate within a safe range for your cardinal tetras.

It also helps to remove any harmful substances that may have built up over time from fish waste, uneaten food, or decaying plant matter. Additionally, replacing old water with new can help to replenish essential minerals and trace elements that are necessary for proper fish and plant health and growth.

Filtration System

A good filtration system in a Cardinal Tetra tank is essential for the health of the fish and other inhabitants. The filter helps to keep the water clean and clear, which is important for the long-term health of your fish.

The main job of a filter is to remove fish waste, debris, and other substances from the water. These substances can be harmful to fish and will lead to fatal events if not removed.

Overall, investing in a good quality filtration system for your Cardinal Tetra tank is essential for maintaining healthy water conditions and keeping your fish healthy and happy.

When selecting a filter, consider the size of your tank and the number of fish and plants you have. If you have a small tank with only a few Cardinals, then a hang-on-back filter may be sufficient. However, if you have a larger tank with more fish or you want to ensure the health of your fish, then a canister filter may be more appropriate.

Common Diseases and Prevention

Diseases are the main reason we do not recommend this fish for beginners. Cardinal tetras are very easy to care for but they are also very sensitive and poor water conditions can cause different diseases in these beautiful fish. 

They are especially prone to a variety of aquarium diseases, such as Ich (Ichthyophthirius multifiliis) and other bacterial infections. Bacterial infections can cause red streaks or ulcers on the skin, fin rot, and decreased appetite. 

These types of infections can be difficult to treat and often require antibiotics. If not treated promptly, they can lead to death or poor quality of life for the fish. 

It is important for any aquarist housing Cardinal Tetras to regularly check their water parameters and keep an eye out for signs of disease in order to prevent serious problems from developing.

To prevent diseases in an aquarium, it is important to keep the water clean and maintained with regular water changes. At the same time, it is also important to quarantine any new fish before adding them to the aquarium and to avoid overcrowding. Additionally, it is important to feed the fish a balanced diet but not overfeed them.

Diet and Feeding Requirements

Cardinal Tetras are primarily omnivores and usually feed on small insects, invertebrates, and plant matter in the wild. They can eat any small creature that fits in their tiny mouth including larval stages of insects, crustaceans, worms, and zooplankton. They also consume algae, diatoms, and detritus. 

In the wild, these fish use their sharp eyesight to spot food in the water column or among plants and debris. They then use their slender bodies to quickly dart forward and capture their prey.

In captivity, you can feed your Cardinal Tetra a varied diet of high-quality flake food, small pellets, and frozen or freeze-dried foods like brine shrimp, daphnia, bloodworms, and mosquito larvae.

Dry processed fish foods are designed to provide a balanced, nutritionally complete diet for the fish. They typically contain a variety of ingredients such as proteins, fats, carbohydrates, vitamins, minerals, and other essential components. 

Some foods also contain color enhancers that can help the cardinal tetras develop deeper colorations. 

Frozen aquarium fish foods are a great way to add some diversity to your Cardinal Tetra’s diet. These foods are packed with proteins, vitamins, and minerals that will help the fish develop a better immune system. 

Breeding Cardinal Tetra

Cardinal tetra is an attractive and vibrant species of fish that can be bred in an aquarium. To successfully breed them, you must first ensure the water is clean and the temperature is slightly up. The pH level in the tank should be slightly lower than normal to trigger spawning. 

Next, you should provide plenty of dense vegetation in the tank and no other fish should be present. Other fish or snails can eat the eggs so the breeding parents should be in a separate tank with no tankmates. 

The males will then start chasing the females around until the female is ready to lay her eggs. After spawning, it is important to remove any adult fish from the tank as they may eat their own eggs or fry (baby cardinal tetras).

Finally, provide newly hatched fry with plenty of food such as baby brine shrimp or powdered algae. With proper care and attention, these baby fish will grow very fast and become the next generation of cardinals in your aquariums. 

Cardinal Tetras are prolific egg layers, laying up to 500 eggs at a time. They prefer to lay their eggs in the roots of plants or other vegetation, where they will be protected from predators.

The eggs hatch within 24 – 36 hours after they are laid, and the fry will become free-swimming within four days. The fry is very small and needs very fine food such as infusoria or powdered food to survive. 

Tank Mates

Cardinal tetras are peaceful and mild-mannered fish that generally get along well with other tank mates, as long as they are of a similar size. They can be kept with other peaceful fish but should not be kept with larger species that might bully them or view them as prey.

A larger tank size will enable cardinal tetras to school together and stay safe when slightly aggressive fish are present. This will also force them to school tighter and sway in the aquarium in a much better fashion. 

As a general rule, Cardinal tetra fish should be kept with other similar-sized fish that are peaceful. Keeping them with similarly sized fish will help to create a stress-free environment where they can feel safe and secure. This in turn will help to promote their health and overall well-being.

Considering these points, here are our top recommendations for tank mates for Cardinal Tetras:

School of Cardinal Tetras
School of Cardinal Tetras


Keeping Cardinal Tetra fish in an aquarium is a great way to add color and activity to your tank. They are easy to care for and have a peaceful demeanor, so they will get along with other fish in the aquarium. What makes them unique is that they have a bright red line running along their sides, which adds a splash of color to any aquarium. 

They also enjoy swimming in schools, so it’s best to keep at least six together. With proper care and the right environment, these beautiful fish can provide hours of enjoyment for years to come.

Paracheirodon axelrodi
Microsatellite markers for the cardinal tetra
Tolerance to temperature, pH, ammonia and nitrite in cardinal tetra, Paracheirodon axelrodi, an Amazonian ornamental fish