Cardinal Tetra – Care, Tank Mates & Full Details!

Cardinal tetra, scientifically known as Paracheirodon axelrodi, is a small yet delightful member of the tetra fish family. Growing up to two inches, these freshwater fish are renowned for their striking colors and peaceful demeanor.

In addition, their active lifestyle and compatibility with other species make them ideal candidates for community tanks.

The cardinal tetra, a vibrant specimen of freshwater tetra fish, has captivated aquarists across the globe with its dazzling colors and radiant neon blue stripes.

Frequently confused with neon tetras due to their similar vibrant appearance, cardinal tetras offer an added allure with their captivating colors and graceful swimming patterns.

Cardinal tetras are also popularly known as red neon tetra and scarlet characin. Their scientific name, Paracheirodon axelrodi, pays homage to Dr. Herbert R. Axelrod, a notable tropical fish enthusiast and publisher.

In this comprehensive guide, we delve into the intricate details of cardinal tetra care, from their preferred habitats to their feeding routines, ensuring you have all the information you need to maintain a thriving community of these beautiful fish in your aquarium.

Cardinal tetra

Quick Stats About Cardinal Tetra

Scientific name: Paracheirodon axelrodi
Common names: Cardinal tetra, red neon tetra, scarlet characin
Distribution: Brazil, Colombia, Venezuela
Size: 2 inches
Life expectancy: 4–5 years
Color: Bright coloring, red, iridescent blue stripe
Diet: Omnivore
Temperament: Peaceful
Minimum tank size: 20 gallons
Temperature: 73–81°F (23–27°C)
pH: 4.6–6.2
Hardness: Up to 4 dGH
Care level: Intermediate
Breeding: Egg layers

Cardinal Tetra Appearance

At first glance, the cardinal tetra (Paracheirodon axelrodi) leaves a lasting impression with its stunning, jewel-like coloration.

A display of cardinal tetras, in their radiant blue and red hues, easily brings a touch of the Amazon to any aquarium.

The cardinal tetra boasts a vivid neon blue stripe that extends from its snout to its tail, providing a delightful contrast to the fiery red that runs along its lower body.

This stunning display is complemented by translucent fins and a sleek, spindle-shaped body, aptly adapted for fast and agile swimming.

The varying hues of cardinal tetras are even more pronounced under different lighting conditions. Interestingly, they lose their brilliant coloration at night, a phenomenon that returns with daylight.

However, any loss of color during the day may indicate stress or a health issue.

Sexual dimorphism is subtle yet noticeable in cardinal tetras. Females are generally larger with a more rounded belly, while males possess a tiny hook on their anal fin.

Varieties such as the albino and gold cardinal tetras add to the fascinating diversity of this species.

Natural Habitat of Cardinal Tetra

The natural habitat of the cardinal tetra is as fascinating as its striking appearance. These fish are native to the blackwater streams and tributaries of the Amazon basin, specifically within the Orinoco and Negro River drainages.

Here, the water is soft and acidic, stained dark by tannins leached from decaying plant matter.

These shadowy waters, with their substrate of branches, roots, and leaf litter, offer an ideal environment for the cardinal tetra.

The dense overhead foliage shields the water from direct sunlight, creating a dimly-lit, serene habitat that these fish prefer.

Replicating this natural habitat within an aquarium encourages the cardinal tetra’s best coloration and behavior.

Key elements include dim lighting, soft water, and plenty of hiding spots among roots and leaf litter.

Origin and Distribution of Cardinal Tetra

The cardinal tetra was first discovered in the mid-20th century by Dr. Leonard P. Schultz, a renowned ichthyologist.

The species was later named in honor of Herbert R. Axelrod, a significant figure in the aquarium hobby.

These fish are found in large numbers across Brazil, Colombia, and Venezuela.

In the wild, they inhabit the slow-flowing blackwater creeks and tributaries, thriving in the warm, soft, and acidic waters of these tropical environments.

Although cardinal tetras are bred in captivity, a significant portion of the fish available in the aquarium trade is wild-caught, making sustainable and responsible fishkeeping practices essential for this species.

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Growth, Size & Lifespan of a Cardinal Tetra

Cardinal tetras are small, yet captivating freshwater fish. On average, they grow to about two inches in length, with females tending to be slightly larger than males.

Despite their small size, a well-maintained group of these fish can make a striking visual impact in an aquarium.

The average lifespan of a cardinal tetra in captivity is around four to five years, although some individuals have been known to live for up to a decade.

This lifespan significantly contrasts with their average lifespan of one year in the wild, largely due to predation and disease.

The key to a long, healthy life for a cardinal tetra involves providing a well-maintained tank with stable water parameters, a balanced diet, and regular partial water changes.

With proper care, these enchanting fish can provide a vibrant, dynamic display in your aquarium for up to 5 years, sometimes even longer.

Cardinal Tetra Behavior and Temperament

Cardinal tetras are known for their peaceful and sociable nature, making them a perfect addition to community tanks.

They exhibit schooling behavior, meaning they prefer to swim in groups. The vibrant display of a school of cardinal tetras moving in unison is truly a sight to behold.

These fish are active during the day and can often be seen exploring their surroundings or darting playfully around the tank.

Their docile temperament means they rarely show aggression towards other species, though they may become slightly territorial during the breeding season.

Tank Setup for Cardinal Tetras

Creating a suitable environment for your cardinal tetras is crucial to their health and happiness. An ideal setup replicates their natural habitat as closely as possible, providing them with plenty of space to swim and explore.

Tank Size

A cardinal tetra requires a minimum tank size of 20 gallons. Given their schooling nature, it’s best to keep at least six tetras together, with an additional 2 gallons of space per fish to ensure they have plenty of room to swim freely.


Choose a dark, sandy substrate for your cardinal tetra tank. This mimics their natural environment and also enhances their vibrant colors.

Decorations and Hiding Spots

Incorporate plenty of hiding spots into your tank setup. Driftwood, rocks, and caves are excellent options. These provide shelter for your tetras, making them feel safe and secure.

Water Parameters

Cardinal tetras thrive in soft, slightly acidic water. Maintain a pH level between 4.6 and 6.2 and a water hardness of up to 4 dGH.

The ideal temperature range for these fish is between 73°F and 81°F (23°C and 27°C).

Filtration and Aeration

These fish are accustomed to slow to moderate currents in their natural habitat, so a filtration system that generates a similar current is ideal.

While cardinal tetras can tolerate low oxygen levels, an air pump or bubbler can ensure proper oxygenation and aid in maintaining water quality.


Cardinal tetras prefer dimly lit conditions. Harsh or overly bright lighting can stress them and dull their vibrant coloration.

If your tank is brightly lit, consider adding floating plants to provide shaded areas.

Tank Mates

Given their peaceful disposition, cardinal tetras get along well with other docile and similarly-sized fish species.

Good companions include small tetras, pencil fish, hatchet fish, rasboras, dwarf gouramis, barbs, and corydoras catfish.


Cardinal tetras are omnivorous and enjoy a varied diet. Feed them a mix of high-quality flake food, pellets, and live or frozen foods like bloodworms, daphnia, and brine shrimp.

Occasional vegetable matter, such as blanched peas or zucchini, can also be included in their diet.

Monitoring Health

Regularly observe your cardinal tetras for any signs of illness, such as changes in behavior, color, or appetite.

Common diseases include ich, fin rot, and neon tetra disease. Always quarantine new fish before adding them to your tank to prevent disease introduction.

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Tank Maintenance for Cardinal Tetras

Maintaining a clean and healthy tank is crucial to the wellbeing of your cardinal tetras.

Regular maintenance not only keeps your tank looking its best, but also ensures optimal conditions for your fish. Below, we’ll delve into the specifics of maintaining a cardinal tetra tank.

Regular Water Changes

Regular water changes are an essential part of tank maintenance. Over time, waste materials can build up in your tank, leading to a rise in harmful substances such as nitrites and ammonia.

By changing 25-30% of the water weekly, you can help to keep these toxins at a manageable level.

When changing the water, it’s also important to match the temperature and pH of the new water with the existing tank water.

This helps to prevent any sudden changes that could stress your fish.

Cleaning the Tank and Decorations

Regularly cleaning your tank and its decorations helps to prevent the build-up of algae and harmful bacteria.

Use a suitable aquarium vacuum to clean the substrate and remove any uneaten food or waste material.

Decorations should also be cleaned to prevent algae overgrowth. However, avoid using any harsh chemicals or soap, as these can harm your fish.

Instead, opt for warm water and a soft brush to clean any decorations.

Filter Maintenance

Your filter plays a crucial role in maintaining water quality by removing waste and harmful chemicals. It’s important to clean your filter regularly to ensure it functions optimally.

However, be mindful to not remove all the beneficial bacteria that live in the filter and aid in breaking down waste.

Typically, a rinse in the water removed during a water change is sufficient to clean the filter without destroying the beneficial bacteria.

Always check the manufacturer’s instructions for specific guidance.

Monitor Fish Health

As part of your maintenance routine, keep a close eye on your cardinal tetras. Look out for any changes in their behavior, color, or eating habits, as these could be early signs of illness.

By catching any health issues early, you can take steps to treat your fish and prevent any diseases from spreading to other tank inhabitants.

Consulting with a vet or an aquarist expert can provide you with the necessary guidance and treatment options.

In summary, regular maintenance and monitoring are key to a thriving cardinal tetra tank.

By keeping up with these tasks, you’ll ensure your fish live a long, healthy life in a clean and balanced environment.

Acclimating Cardinal Tetras

Introducing new cardinal tetras to your aquarium requires a delicate process known as acclimation.

This process helps your new fish adapt to their new environment and minimizes stress, which is vital for their survival and overall health.

When your new cardinal tetras arrive, they will likely be in a bag filled with water. Start by floating this bag in your tank without opening it.

This step allows the water inside the bag to gradually match the temperature of your tank, typically over a period of 15-20 minutes.

Next, slowly introduce some water from your tank into the bag. This helps the fish adjust to the water chemistry of your tank.

Over the next 30-45 minutes, gradually add more tank water into the bag.

After this period, gently net the fish from the bag and release them into the tank. Avoid pouring the water from the bag into your tank, as it may contain waste or disease.

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Cardinal Tetras Diet and Feeding

Cardinal tetras are omnivorous by nature, requiring a balanced diet of both plant and animal matter.

A diverse diet not only fulfills their nutritional needs but also keeps them active and enhances their vibrant colors.

Dry Foods

Quality dry foods like flakes and micro pellets form a good basis for the cardinal tetra’s diet. They are nutritionally balanced and easy to feed. However, be mindful of the size of the food; cardinal tetras have small mouths, so it’s important that the food is small enough for them to eat.

Live and Frozen Foods

Cardinal tetras also benefit from the inclusion of live and frozen foods in their diet. These could include brine shrimp, daphnia, and bloodworms. Live and frozen foods are high in protein and mimic what cardinal tetras would eat in their natural habitat.

Vegetable Matter

Although cardinal tetras are not primarily herbivores, including some vegetable matter in their diet is beneficial. This could be in the form of blanched vegetables like zucchini or specialized vegetable-based fish foods.

Feeding Schedule

Cardinal tetras should be fed 1-2 times daily, with only as much food as they can consume in 2-3 minutes. Overfeeding can lead to water quality issues and health problems for your fish.

In conclusion, a varied diet and proper acclimation process are essential for the wellbeing of your cardinal tetras.

By providing these, you’ll ensure that your fish remain healthy, active, and vibrant in your aquarium.

Cardinal Tetras Tank Mates

Cardinal tetras are peaceful community fish, and their vibrant colors make them an excellent addition to a community aquarium.

They thrive best with other peaceful, similarly-sized species.

When choosing tank mates for your cardinal tetras, consider these options:

  1. Neon Tetras: Sharing similar needs and peaceful dispositions, neon tetras make for an excellent tank mate for cardinal tetras. They also add a splash of color to your aquarium.

  2. Harlequin Rasboras: These fish are peaceful and easy to care for, making them a great match for cardinal tetras.

  3. Corydoras Catfish: These bottom-dwelling fish won’t compete with cardinal tetras for space and can help keep the tank clean.

  4. Dwarf Gouramis: Known for their calm nature, dwarf gouramis can comfortably share a tank with cardinal tetras.

  5. Cherry Shrimp: These small invertebrates won’t bother your cardinal tetras and add variety to your aquarium.

  6. Otocinclus Catfish: Like the Corydoras, these fish are peaceful and keep to the lower levels of the tank.

  7. Hatchetfish: These surface dwellers are peaceful and will not compete for space with the mid-water swimming cardinal tetras.

  8. Ghost Shrimp: These are peaceful towards fish and can coexist easily with cardinal tetras.

Tank Mates to Avoid

While cardinal tetras can coexist with many species, certain types of fish should be avoided.

These include:

  1. Cichlids: Most types of cichlids are aggressive and can harm or eat smaller fish like cardinal tetras.

  2. Betta Fish: While beautiful, bettas can be territorial and aggressive, posing a threat to the peaceful cardinal tetra.

  3. Large Catfish: Larger species like the Pictus Catfish may view smaller fish as prey.

  4. Arowana: These fish are large predators and will likely eat smaller fish like cardinal tetras.

  5. Oscars: Known for their aggressive temperament, Oscars are not suitable tank mates for cardinal tetras.

Breeding Cardinal Tetras and Fry Care

Breeding cardinal tetras can be a rewarding but challenging experience.

Here’s a step-by-step guide to help you navigate the process:

Preparing for Breeding

  1. Set Up a Breeding Tank: A 10-gallon tank with a sponge filter, heater, and dim lighting is ideal. Use dark substrate and provide plenty of plants for the eggs to fall into and remain hidden from the parents.

  2. Condition the Parents: Feed the breeding pair high-quality live or frozen foods to get them in prime breeding condition.

Breeding Process

  1. Introduce the Breeding Pair: Once conditioned, transfer the pair to the breeding tank.

  2. Spawning: If the conditions are right, the female will lay her eggs on the plant leaves or on the substrate, and the male will fertilize them.

Fry Care

  1. Remove the Parents: After spawning, remove the parents to prevent them from eating the eggs.

  2. Incubation: The eggs will hatch in about 24 hours. They will remain attached to their hiding spot for a few more days, absorbing their yolk sac.

  3. Feeding the Fry: Once they start swimming freely, feed them infusoria or commercially prepared fry food. As they grow, you can introduce micro-worms and baby brine shrimp.

  4. Water Changes: Regular partial water changes are essential to prevent the build-up of toxins.

  5. Observation: Keep a close eye on the fry. Monitor their growth and watch out for any signs of illness or stress. Regular observation can help you ensure that they’re developing properly and staying healthy.

  6. Gradual Introduction to the Main Tank: Once the fry have grown large enough that they won’t be seen as food by other fish, you can gradually introduce them into the main tank. This should be done slowly and carefully to minimize stress.

Breeding cardinal tetras requires patience and careful attention to detail.

However, with the right approach, it can be an incredibly rewarding experience, leading to a new generation of these stunning fish to enhance your aquarium.


Signs of Stress in Cardinal Tetras

Cardinal Tetras are generally hardy fish, but they can exhibit signs of stress when they aren’t in the right conditions.

Identifying these signs early can help you take corrective measures promptly and keep your fish healthy.

  1. Change in Color: Cardinal tetras are known for their vibrant colors. However, stress can cause these colors to fade. If your fish’s colors seem less vibrant than usual, it might be experiencing stress.

  2. Lack of Appetite: A sudden decrease in appetite can indicate stress. If you notice your cardinal tetra eating less or not eating at all, this could be a cause for concern.

  3. Erratic Swimming: Cardinal tetras usually swim in a calm, deliberate manner. If you see your fish darting around the tank or swimming erratically, it may be stressed.

  4. Isolation: While cardinal tetras are schooling fish and prefer to swim in groups, stressed individuals may isolate themselves from the rest of the school.

Common Health Issues and Treatments for Cardinal Tetras

Cardinal tetras are generally healthy fish, but they can be susceptible to certain health issues, like any other aquatic species.

Here are a few common problems:

  1. Ich: Also known as white spot disease, Ich is a common ailment among aquarium fish. It appears as white spots on the fish’s body and fins. Treatment typically involves raising the water temperature and using a specialized Ich treatment solution.

  2. Fin Rot: This bacterial infection causes the fish’s fins to fray and discolor. Good water quality is crucial for prevention, and antibiotics can be used for treatment.

  3. Fungal Infections: Fungal infections can lead to cotton-like growths on the fish. These can be treated with antifungal medications.

  4. Parasitic Infections: Parasites can cause a range of symptoms, from lethargy to loss of appetite. Anti-parasitic medications are generally effective for treatment.

Remember, prevention is always better than cure. Regular tank maintenance, monitoring water parameters, and feeding a balanced diet can help prevent most of these health issues.

Additional Tips for a Healthy Aquarium

  1. Regular Maintenance: Regular water changes and tank cleaning are crucial for maintaining a healthy environment for your fish.

  2. Monitor Water Parameters: Keep an eye on the water parameters, like pH, temperature, and ammonia levels. Any drastic changes can cause stress to your fish.

  3. Balanced Diet: Feed your fish a balanced diet to ensure they get all the necessary nutrients. A mix of high-quality flakes or pellets and occasional live or frozen food can provide a well-rounded diet.

  4. Observation: Regularly observe your fish for any signs of illness or stress. Early detection can make treatment more effective.

Should You Get a Cardinal Tetra for Your Aquarium?

Cardinal tetras can make a fantastic addition to your aquarium. Their vibrant colors and active behavior can bring life and beauty to your tank.

They’re also relatively easy to care for, making them a good choice for both novice and experienced aquarium keepers.

However, it’s essential to consider their specific needs, like a large tank for schooling and specific water parameters.

If you’re ready to provide the right environment for these stunning fish, then cardinal tetras could certainly be a great choice for your aquarium.

Conservation Status of Cardinal Tetras

Cardinal Tetras are widely distributed throughout the wild, especially in the Orinoco and Negro River basins in South America. They are not listed as threatened or endangered on the IUCN Red List.

They are quite abundant in their native habitats, and responsible collection methods for the aquarium trade don’t seem to have a significant impact on their overall population.

However, it’s always essential to support suppliers who prioritize sustainable and responsible fishing practices.

This helps maintain healthy fish populations and protects the biodiversity of our planet’s waterways.

Availability & Pricing

Cardinal Tetras are popular in the aquarium trade, making them readily available in many pet stores and online retailers.

Their price can vary based on factors like size, color vibrancy, and overall health, but they’re generally quite affordable.

You can typically expect to pay a few dollars per fish. Keep in mind that these are schooling fish, so it’s best to buy them in groups, which can affect the overall cost.

Frequently Asked Questions About Cardinal Tetras

1. Can Cardinal Tetras Live Alone?

No, Cardinal Tetras are schooling fish and prefer to live in groups. A minimum group of six is often recommended, but they’ll be happier in larger schools.

2. How Long Do Cardinal Tetras Live?

With proper care, Cardinal Tetras can live for up to five years in captivity.

3. Are Cardinal Tetras Easy to Care For?

Yes, Cardinal Tetras are generally easy to care for, making them suitable for both novice and experienced aquarists. However, they do require specific water conditions and a well-maintained aquarium to thrive.

4. What Do Cardinal Tetras Eat?

Cardinal Tetras are omnivores and will eat a variety of foods. A balanced diet includes high-quality flakes or pellets and occasional treats of live or frozen foods.


Cardinal Tetras, with their vibrant colors and active nature, can make a fantastic addition to your freshwater aquarium.

Their relatively easy care, hardy nature, and stunning looks make them a popular choice among hobbyists. Remember, they thrive best in a well-maintained environment that mimics their natural habitat.

Like any pet, they require commitment and care. So, if you’re prepared to provide the right tank conditions, a balanced diet, and regular maintenance, Cardinal Tetras could indeed be the perfect new addition to your aquatic family.