Cardinal tetra

Cardinal tetra

Paracheirodon axelrodi

MAINTENANCE: EASY / CARE: EASY / REPRODUCTION: DIFFICULT / COST: REASONABLE

This is one of the best-selling fish in the world. With its electric blue and red colours, the cardinal is the emblem of aquarists. Found in community aquaria (a mixed species group of compatible fish) or in the Amazonian basin, it prefers freshwater and dense vegetation.

Map of Brazil locating the River Neqro, a tributary of the Amazon.

FACT SHEET

Common name: Cardinal or cardinal tetra. Family: Characidae. Origin: River Negro and its tributaries. Natural habitat: It lives near banks and in the tangles of branches and roots. Size: 4 to 5 cm. Sexual differences: The mature female presents a full under-belly. Behaviour: Lives in shoals, quiet and unaggressive.

 

The waters that the cardinal comes from are very soft, the colour of tea, turned amber and acid by the decomposition of vegetable matter, but, even so, crystal clear. A long way from its origins, the cardinal tetra becomes acclimatised surprisingly quickly to the conditions in an aquarium. Fished by the million in their natural environment, cardinal tetras are rarely bred by professional breeders. In the tanks where they are sold they are often mistaken for the neon tetra (Paracheirodon innesi), whose red band stops at the abdomen.

In the aquarium

The cardinal tetra is the classic example of the community fish (living in shoals). It is a good idea to keep at least ten individuals in a 60-litre tank. In a larger volume, 150 to 200 litres, a shoal of 30 to 40 fish moving around among the plants can look effective. Even though it does not encounter any problems with tap water (which is often hard), it prefers soft water. For the fish to do well, the tap water must be half diluted with rain water or demineralized water (available at many dealers). It is advisable to change a minimum of 20% of the volume of the aquarium every month.

The aquarium must be densely planted. Keeping to its South American origins, choose Echinodorus with its tall, oblong leaves for the middle of the aquarium, in the background clumps of Cabomba aquatica or Bacopa monnieri. It does not matter much about the floor, because it is a fish which moves around in open water.

Feeding

Although it is an omnivore, the cardinal tetra prefers small living prey, like bloodworms, Cyclops (small freshwater crustaceans about 0.5 mm long) or Artemia. Manufactured food is accepted, as long as it is in small pieces suited to the size of its mouth. It quickly reaches its adult size of 5 cm.

Breeding

The cardinal tetra is mature at one year. It is a fish which lays its eggs in open water and is difficult to breed. The females can be recognised by the fullness of their belly. So in a shoal it is easy to select a pair for isolating in a small, very densely planted tank devoid of light. The water must be made acid by a supply of carbon dioxide served by a pH meter set between 4.5 and 5. There are other methods for lowering the pH which are more delicate and less durable, such as the addition of phosphoric acid. The pair lay 200 to 500 eggs in the middle of the plants. When the parents have moved out of the way, the young fish hatch after five days. They then feed on micro-organisms

The waters that the cardinal comes from are very soft, the colour of tea, turned amber and acid by the decomposition of vegetable matter, but, even so, crystal clear. A long way from its origins, the cardinal tetra becomes acclimatised surprisingly quickly to the conditions in an aquarium. Fished by the million in their natural environment, cardinal tetras are rarely bred by professional breeders. In the tanks where they are sold they are often mistaken for the neon tetra (Paracheirodon innesi), whose red band stops at the abdomen.

Life in the aquarium
Maintenance	In a community aquarium, or better still with fish from the same region. Minimum volume, 60 litres for 10 fish.
PH	Slightly acid, 6 to 6.5. For breeding, lower to between 4.5 and 6.
Water hardness	It tolerates hard water, but prefers soft water (4 dH).
Temperature	Ideally 25 to 27°C.
Changing the water	At least 20% per month.
Food	Small prey, preferably alive. It accepts flakes and frozen food.
Reproduction	Difficult.
Compatibility	Can be kept with other fish of similar size. Avoid large angelfish and discus.
Life expectancy	From 2 to 3 years.
Comments	Cardinal tetras are at home in dense plant cover and in a shoal of at least 10 individuals.

The cardinal tetra usually lives in shoals.