Cardinal Tetra

Also known as: Paracheirodon axelrodi

The Cardinal Tetra is a small, vibrant freshwater fish native to the blackwater streams of the Amazon Basin. The Cardinal Tetra originates from Orinoco and Negro River basins in Brazil, Colombia, and Venezuela, reaches Adult size: 3.5 cm in captivity, typically lives 4-5 years, and is kept at 23-27°C (73-81°F). Individual fish vary, so treat this as a general guide rather than a guarantee.

Species at a glance

Origin: Orinoco and Negro River basins in Brazil, Colombia, and Venezuela
Adult size: Adult size: 3.5 cm (1.4 inches)
Life span: 4-5 years
Temperament: Peaceful, schooling fish
Tank size: Minimum 40 liters (10.5 gallons) for a group of 6-8
Water temp: 23-27°C (73-81°F)
pH range: pH 4.0-6.0
Diet: Omnivorous; accepts high-quality flakes, micro pellets, and live/frozen foods like brine shrimp and daphnia
Other names: Paracheirodon axelrodi

About the Cardinal Tetra

The Cardinal Tetra is a small, vibrant freshwater fish native to the blackwater streams of the Amazon Basin. It is renowned for its striking iridescent blue stripe running from nose to tail and a vivid red lower body, making it one of the most popular aquarium species. Unlike the similar Neon Tetra, the red coloration extends the full length of the body. Cardinal Tetras are highly social and thrive in large, well-planted schools.

Lifespan and health

With optimal care, Cardinal Tetras typically live 4-5 years in captivity, though some individuals may reach 6 years under exceptional conditions. Lifespan is heavily influenced by water quality, diet, and stress levels; poor conditions such as high nitrates, fluctuating pH, or inadequate schooling can shorten lifespan significantly. They are sensitive to sudden changes in water parameters and require stable, soft, acidic environments to thrive long-term. Common health issues include Ich (white spot disease), often triggered by stress or temperature drops below 22°C (72°F), and fungal infections from poor water quality or injury. They are also susceptible to bacterial infections like Columnaris if exposed to organic waste or overcrowding. Preventative measures include maintaining zero ammonia and nitrite, keeping nitrates below 20 ppm, quarantining new fish, and avoiding overfeeding. Regular observation for lethargy, clamped fins, or loss of color is essential for early detection.

Overview

Care and tank setup

Cardinal Tetras require a densely planted aquarium with subdued lighting and plenty of hiding spots using driftwood, leaf litter, and plants like Java moss or Anubias. A dark substrate enhances their coloration and reduces stress. Minimum tank size is 40 liters (10.5 gallons) for a school of 6-8, but 60+ liters (16+ gallons) is ideal for larger groups. Water must be soft and acidic, with peat filtration or Indian almond leaves recommended to replicate natural blackwater conditions. Avoid strong currents; gentle flow from a sponge filter is preferred. Feeding should occur 2-3 times daily with small amounts they can consume in under 2 minutes. Offer a varied diet: high-quality micro pellets or flakes as staple, supplemented 2-3 times weekly with live or frozen foods such as baby brine shrimp, daphnia, or cyclops. Overfeeding must be avoided due to their small size and sensitive digestive systems. Perform 25% water changes weekly using aged, soft water matched to tank parameters to maintain stability. Tankmates should be peaceful, small, and similarly tempered. Ideal companions include other small tetras (e.g., Ember, Rummy-nose), Corydoras catfish, small rasboras, and peaceful dwarf cichlids like Apistogramma. Avoid larger, aggressive, or fin-nipping species such as barbs or large cichlids. Never keep with predators that can fit them in their mouth. A school of at least 8-10 Cardinal Tetras is recommended to reduce stress and encourage natural shoaling behavior.

Adding a Cardinal Tetra? Research the species’ adult size and temperament carefully, quarantine new fish before introducing them to your tank, and buy from reputable aquarium stores or breeders.

Breed information on this page is based on the Wikipedia article on the Cardinal Tetra, supplemented with additional research. Reviewed for accuracy.