Cardinal Tetra

Species NameParacheirodon axelrodi
Common NameCardinal Tetra
Care LevelIntermediate
LifespanUp to 5 years
Adult Size1.5-2 inches (3.8-5 cm)
Minimum Tank Size20 gallons
Temperature73°F – 81°F (23°C – 27°C)
Water ConditionspH 5.5-7.5, Soft to medium hardness

About the Cardinal Tetra – Species Summary

The Cardinal Tetra, scientific name Paracheirodon axelrodi, is a small and vibrant freshwater fish native to the blackwater rivers of South America, predominantly found in the Orinoco and Upper Rio Negro river basins. Revered for its splendid neon blue and red coloration that spans the length of its body, the Cardinal Tetra has made its mark as a staple in many freshwater aquariums around the world. Beyond its beauty, this species is particularly admired for its schooling nature, where it often moves in harmonious, coordinated groups, adding dynamic motion to any aquatic environment.

Their adaptability to different environments, paired with their peaceful nature, makes them a preferred choice among aquarists. However, due to their sensitivity to water conditions, they are best suited for intermediate to advanced aquarists willing to provide the necessary care and stability.

Cardinal Tetra Lifespan

With proper care and an optimal environment, Cardinal Tetras can live up to 5 years. Their lifespan in the wild is typically shorter due to predation and environmental challenges. In a well-maintained aquarium, free from stressors and with a balanced diet, these tetras can thrive and illuminate the tank with their vivid presence for several years.


One of the most striking features of the Cardinal Tetra is its vibrant coloration. The anterior half showcases a brilliant blue hue, while the posterior half is dominated by a rich red. This stark contrast is accentuated by a thin silver line that separates the two primary colors. Their small, torpedo-shaped body and translucent fins further enhance their elegant swimming style, making them a visual delight for any observer.

Average Size

Adult Cardinal Tetras usually reach a size between 1.5 to 2 inches (3.8 to 5 cm). They are relatively small fish, which makes them ideal for community tanks. Their size combined with their schooling nature often encourages aquarists to keep them in larger groups to truly appreciate their synchronized swimming patterns.

Cardinal Tetra Care

Tank Size

A minimum tank size of 20 gallons is recommended for Cardinal Tetras. Given their preference to school, a larger tank size allows them to swim freely, display natural behaviors, and thrive in groups of 6 or more.

How To Set Up Their Tank

To replicate their natural habitat, use dark substrate combined with driftwood, roots, and plants like Amazon swords or Java fern. Floating plants can be used to diffuse direct light and provide some shaded areas. Additionally, a good filtration system that provides gentle flow mimics the soft currents of their native waters.

Lighting Requirements

Cardinal Tetras do not have specific lighting needs, but they are known to display their best colors under subdued lighting. Using floating plants or dimmable lights can achieve this effect, enhancing their natural brilliance.


Cardinal Tetras thrive in slightly acidic to neutral water with a pH range of 5.5 to 7.5. Regular water tests are crucial to ensure pH stability and prevent harmful fluctuations.


A stable temperature range between 73°F and 81°F (23°C to 27°C) is ideal. Using a reliable aquarium heater and thermometer ensures that the water remains within this range, offering the tetras a comfortable environment.

Water Parameters

Soft to medium water hardness is best for Cardinal Tetras. Conducting regular water changes and using a good-quality aquarium filter helps in maintaining optimal water quality, free from toxins like ammonia, nitrite, and nitrate.

Disease Potential

Like all aquarium fish, Cardinal Tetras can be susceptible to common diseases like Ich or fin rot. Quarantining new fish and plants before introducing them to the main tank can minimize the risk. Moreover, maintaining clean water, providing a balanced diet, and ensuring stress-free conditions are key preventative measures.

Food & Diet

Cardinal Tetras are omnivores and thrive on a varied diet. High-quality flake food, combined with live or frozen foods such as brine shrimp, daphnia, or bloodworms, ensures they receive all necessary nutrients. Regularly varying their diet not only keeps them healthy but also enhances their coloration.

Behavior and Temperament

Cardinal Tetras are peaceful, schooling fish. They exhibit a fascinating, synchronized swimming pattern, especially when in larger groups. They are typically mid to upper-level swimmers and add a dynamic element to the aquarium with their constant movement.

Tank Mates

Due to their peaceful nature, Cardinal Tetras can cohabit with a variety of similarly tempered species. Ideal tank mates include other tetra species, Corydoras catfish, and small rasboras. It’s essential to avoid larger, aggressive fish that might see the Cardinal Tetra as prey.


Breeding Cardinal Tetras can be challenging due to their specific water requirements. Soft, acidic water is crucial for successful breeding. Once spawning occurs, it’s recommended to remove the parents as they might consume the eggs. After hatching, fry can be fed infusoria or finely crushed flake food until they mature.

Cardinal Tetra FAQs (Frequently Asked Questions)