Cardinal Tetra

The Cardinal Tetra (Paracheirodon axelrodi) is a vibrant, peaceful freshwater fish native to the Orinoco and Rio Negro river basins of South America. Renowned for its brilliant, iridescent blue and unbroken crimson-red horizontal stripes, it is one of the most iconic and highly valued schooling fish in the aquarium hobby. While wild specimens function virtually as annual fish due to dramatic seasonal river fluctuations, they can thrive for 5 to 10 years in a well-maintained home aquarium.

Habitat & Tank SetupSchool Size: Must be kept in groups of at least 6 to 10. Keeping them in smaller numbers causes severe stress and muted coloration.

Tank Size: Minimum 10 to 20 gallons to provide ample swimming room for the school.

Environment: Prefer a heavily planted setup with driftwood, floating foliage, and a dark substrate to mimic their natural blackwater habitats. Subdued, gentle lighting brings out their glowing colors.

Water Parameters

Cardinal Tetras are sensitive to sudden environmental changes and require an established, stable tank environment.

Temperature: 73°F to 81°F (23°C to 27°C)pH Range: 5.5 to 7.0 (They prefer soft, acidic water)Hardness: Very soft to moderately hard water.

Diet & Tank Mates

They are unpicky omnivores. Because they have tiny mouths, feed them bite-sized high-protein foods like high-quality micro-pellets, crushed flakes, Daphnia, or frozen baby brine shrimp.

Because they are timid and completely peaceful, they should only be housed with calm, non-aggressive tank mates. Excellent choices include Corydoras catfish, Otocinclus, small Rasboras, peaceful dwarf cichlids, and freshwater shrimp. Never house them with large fish capable of swallowing them.