Cardinal Tetra Care Guide - Aquarium Setup, Diet & Breeding

The Cardinal Tetra is a small, brilliantly coloured characin with an electric-blue stripe running from the nose to the base of the tail and a vivid red stripe extending across the lower half of the body. Its colours are more extensive than those of the closely related Neon Tetra, creating a striking appearance when the fish move together.

Peaceful and active, Cardinal Tetras are most impressive in a substantial shoal. They spend much of their time in the middle levels of the aquarium, weaving through plants and wood while maintaining close contact with one another. Their schooling behaviour becomes especially expressive in a calm, well-established aquarium.

In the wild, these fish live in warm, soft, acidic waters coloured by tannins from fallen leaves and submerged branches. The resulting habitats are often dimly lit, with dark water and broken shafts of sunlight filtering through the rainforest canopy.

Paracheirodon axelrodi was described in the mid-twentieth century and quickly became one of the most recognisable species in the ornamental fish trade. Its compact size, peaceful nature and intense colour pattern have made it a classic choice for planted and biotope-style community aquariums.

Cardinal Tetras are native to the upper Amazon, Rio Negro and Orinoco drainage systems of South America, occurring mainly in Brazil, Colombia and Venezuela. They inhabit slow-moving, often blackwater tributaries, flooded forest margins and small streams shaded by dense vegetation.

A group of Cardinal Tetras should be kept in an established aquarium of at least 60 litres, with a footprint around 60 by 30 cm or larger. Dense planting, driftwood, leaf litter and shaded areas provide security and echo their forest-stream habitat, while open swimming space should remain available through the centre of the tank. A dark, fine-grained substrate, gentle water movement and subdued lighting help their colours stand out and create a natural blackwater-style setting.

Up to 5 cm (2 inches) in total length. Females are usually slightly larger and deeper-bodied than males.

Cardinal Tetras are omnivores and should receive a varied diet of high-quality small flake, micro-pellets and suitably sized granules. Supplement these foods with frozen or live baby brine shrimp, daphnia, cyclops and mosquito larvae. Small portions offered regularly help ensure that every fish receives food without leaving excessive waste.

Cardinal Tetras are peaceful community fish that suit similarly gentle species such as small rasboras, Ember Tetras, other small tetras, Corydoras, Otocinclus and peaceful dwarf cichlids. They should not be housed with large, predatory or boisterous fish that could swallow them or constantly outcompete them for food, including larger cichlids, aggressive barbs and many predatory catfish.

Cardinal Tetras are egg-scattering fish and are challenging to breed in a home aquarium. Use a separate, dimly lit breeding tank with very soft, acidic water and fine-leaved plants or spawning mops. Condition the adults with small live foods, introduce a pair or group, and remove the adults after spawning because they may eat the eggs. The eggs usually hatch within a day, with free-swimming fry requiring infusoria-sized foods before they can accept newly hatched brine shrimp.

Females are generally a little larger and have a fuller, rounder abdomen, particularly when carrying eggs. Males tend to be slimmer and more streamlined, although the difference can be subtle in young or well-fed fish.