• Scientific Name: Paracheirodon axelrodi
• Synonym: Cheirodon axelrodi, Hyphessobrycon cardinalis
• Common Name: Cardinal Tetra, Large Neon Tetra, Red Neon, Roter Neon, Tetra Cardinal
• Family: Characidae
• Origin: Brazil to Colombia, Venezuela
• Adult Size: 2 inches (5 cm)
• Social: Peaceful, suitable for community tank
• Lifespan:4 years
• Tank Level:Top, Mid dweller
• Minimum Tank Size:20 gallon
• Diet:Omnivore, eats most foods

• Breeding: Egglayer
• Care: Intermediate
• pH:4.6 - 6.2
• Hardness: up to 4 dGH
• Temperature:73-81 °F (23-27 °C)

Origin/Distribution

Originating from South America, this species is found in the Orinoco and Rio Negro tributaries all the way to western Colombia.  Other locations have also reported schools of Cardinals, as the result of fish that have escaped from collectors. Manaus, in northern Brazil, is one such location where clusters of Cardinals have made themselves at home.

Cardinal Tetras favor shaded areas with slow moving or standing waters that are very clear. Living in large schools, it is not unusual to find them in groups numbering into the hundreds. Their native habitat generally has extremely soft, acidic water, often with a pH of 5.

This species was named for the man who discovered it, Dr. Herbert R. Axelrod. Originally knwon by the name scientific name of Cheirodon axelrodias, well as Hyphessobrycon cardinalis, it was eventually given the currently accepted name of Paracheirodon axelrod.

Species currently sold in the aquarium trade now include many captive bred specimens from commercial breeders. These fish are more tolerant of water parameters than wild caught specimens.

Description

Arguably the most popular of the small Tetras, the Cardinal Tetra is similar in appearance to the longtime favorite, Neon Tetra. The two can be distinguished from one another by the red color band that extends the entire length of the body in the Cardinal Tetra. In the Neon the red bad runs from only the mid-body to tail.

The Cardinal Tetra has a brilliant neon blue stripe running from the nose to the tail. Below this blue stripe is a brilliant red stripe. The vivid red coloration bleeds into the tail, which is otherwise transparent, as are the other fins. The underbelly is soft white, setting off this beautifully colored fish.

Adults reach a mature size of up to two inches, and will display the best colors when provided with very soft acidic water.  Males and females show few clear differences, however females will have a somewhat deeper body with a rounder belly.

Tankmates

A peaceful fish, like other Tetra species, they should be kept in schools. Schools should be large, with a half dozen being the minimum size. They are suitable for community tanks, as long as water conditions are favorable, and other species are peaceful.  Other Tetra species, Danios, Rasboras, and small to medium members of the catfish family are suitable. Do not keep with any fish that are known to eat smaller, slim-bodied fish. If the companion fish has a big enough mouth to swallow the Cardinal Tetra, it is not a suitable tank mate.

Habitat/Care

Much like the Neon Tetra, this species requires a mature tank that has soft acidic water. The ideal pH is below 6, and the hardness should not be above 4 dGH. Subjecting this species to water that has a high mineral content is a recipe for poor health and shortened lifespans.  The water temperature can be of a broader range, from 73-81 °F (23-27 °C). More importantly, the water chemistry should be stable. This is not a species that does well in a newly started aquarium.

Lighting should be subdued, and décor darker and more subdued. Floating plants are a good means for moderating the lighting. Although they require some hiding spaces, it is important to provide them with some open swimming area as well.  A well planted tank with a center open space is an ideal habitat for this species.  

Diet

An omnivorous species, the Cardinal Tetra will accept most foods.  For optimal health, they should be fed a good variety of foods, including both dry, frozen, and live foods when possible. All foods should be in small pieces, as they have a small mouth. When conditioning breeders, live foods are important. 

Sexual Differences

Few obvious differences exist between the sexes. However, females are fuller in the body, while males are more slender. Females tend to have a more rounded body.

Breeding

Cardinal Tetras are challenging at best, in home aquaria. A separate breeding tank is important, and must have stable water chemistry.  A pH 5 to 5.5, and very soft water of 3 to 4 dGH or below is essential. The tank should be well stocked with fine-leaved plants, as this species will scatter their eggs on the vegetation.

Lighting must be very low, use floating plants to ensure the tank remains dark. Young fry are highly photo-sensitive. Spawning will occur late in the day or even into the night hours. Several hundred adhesive eggs will be scatted over the plants. The parents will consume the eggs, so they should be removed from the tank once spawning is complete.

In approximately twenty four hours the eggs will hatch and live off the yolk sack for another four to five days. Once the fry are free swimming, feed them infusoria, rotifers, egg yolk, or commercially prepared fry food. Follow this with freshly hatched brine shrimp as the fry grow.