Product Details

Cardinal Tetra – Paracheirodon axelrodi

Overview:

The Cardinal Tetra is one of the most iconic freshwater aquarium fish, famous for its intense electric-blue stripe and full-length crimson red lower body. Paracheirodon axelrodi is a peaceful shoaling species that looks spectacular in mature planted aquariums, especially with dark décor, shaded areas and a large group. It is slightly warmer-water and more blackwater-orientated than the standard Neon Tetra, so it should be kept in stable, mature conditions rather than added to new or unstable aquariums.

Key Identification:

Common Name: Cardinal Tetra
Other Names: Red Neon Tetra, Cardinal Neon, Scarlet Neon Tetra
Scientific Name: Paracheirodon axelrodi
Fish Type: Tetra
Water Type: Freshwater

Natural Range & Habitat:

Cardinal Tetras are native to northern South America, especially the Rio Negro and Orinoco tributary systems. FishBase notes that they occur mainly in shoals in the middle water layers and feed on worms and small crustaceans.

Their natural habitats are typically slow-moving, shaded, soft-water streams and flooded forest margins with roots, leaf litter and submerged vegetation. Tropical Fish Hobbyist reports wild habitat readings with pH below 6.5, sometimes down to 5.5, and temperatures around 23–26°C in natural cardinal habitats.

Appearance & Adult Size:

Cardinal Tetras have a slim, streamlined body with a brilliant blue-green lateral stripe above a vivid red stripe that extends from the head area to the tail. This full-length red stripe is the easiest way to separate them from Neon Tetras, where the red is mostly restricted to the rear half of the body.

Adults usually reach around 3–4 cm, with females becoming slightly fuller-bodied when mature. In settled groups, colour is strongest under subdued lighting, against dark substrate and in clean, low-stress aquariums.

Aquarium Suitability:

This species is ideal for mature planted aquariums, blackwater-style aquascapes and peaceful soft-water communities. Cardinals look especially impressive in groups among fine plants, floating plants, bogwood, botanicals and open swimming lanes. They are not suitable for aggressive communities, large predatory fish, boisterous fin-nippers or immature aquariums with unstable water quality.

Recommended Aquarium Size:

A practical minimum is 60 litres for a small group, with 90 litres or more preferred for a larger shoal and better stability. FishBase recommends group keeping and gives a minimum aquarium length of around 60 cm.

Water Conditions:

Temperature: 24–28°C
pH: 4.5–7.0
Hardness: Soft preferred; very hard water is not ideal
Additional Notes: Cardinal Tetras prefer warm, soft, acidic to neutral water, particularly if wild-caught. Seriously Fish gives a broad pH range of 3.5–7.5, while noting that wild specimens do best in more acidic conditions. Captive-bred or well-acclimated fish can be more adaptable, but sudden changes, high nitrate and immature tanks should still be avoided.

Temperament & Tank Mates:

Aquarium Category: Community Fish

Cardinal Tetras are peaceful shoaling fish and should be kept with calm tank mates that enjoy similar warm, stable conditions. Suitable companions include small peaceful tetras, pencilfish, hatchetfish, dwarf cichlids such as Apistogramma, Cory-type catfish that tolerate warmer water, Otocinclus, small plecs and gentle rasboras in compatible water.

Avoid angelfish large enough to eat them, predatory fish, aggressive cichlids, large gouramis, fin-nipping barbs and very boisterous tank mates. Keep in a group of at least 8, with 10–20 or more preferred for the best colour, confidence and shoaling effect.

Feeding:

Cardinal Tetras are small omnivorous micro-predators. Offer fine flakes, micro pellets and small granules as the staple diet. Supplement with frozen or live foods such as daphnia, cyclops, baby brineshrimp, mosquito larvae and finely chopped bloodworm. Research on wild Cardinal Tetra diet describes them feeding heavily on tiny invertebrates associated with submerged litter, roots and aquatic plants.

Behaviour in the Aquarium:

This species occupies the middle water levels and moves in a loose shoal. In a calm aquarium, the group will spread through open areas and plants, tightening together when startled. Cardinals show their strongest colour in larger groups, under subdued lighting and when they are not being chased or outcompeted by faster fish.

Care Notes:

Add Cardinal Tetras only to a fully cycled, mature aquarium. Acclimate carefully, especially if moving them into softer or more acidic water. Keep nitrate low, avoid sudden changes and provide a secure lid, as small tetras can jump when startled. FishBase notes that captive breeding is possible but difficult, and many specimens in the aquarium trade have traditionally been wild-caught from Rio Negro and Orinoco tributaries.

Recommended For:

Beginner to intermediate

Availability:

Common / Wild-caught and captive-bred depending on supplier

Image Disclaimer:

All images are a visual representation of the fish you will receive, made to be as accurate as possible. Natural variation in size, colour, pattern and markings can occur between individual fish.