Cardinal Tetras are an active schooling fish and they live well in a peaceful community aquarium. Although it's difficult to breed in captivity, Tetras remain a very popular aquarium fish.
Cardinal Tetra: Basics
- 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 a 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 to 81 F (23 to 27 C)
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, likely comprised 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. They live in large schools, and 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 after the man who discovered it—Dr. Herbert R. Axelrod. Originally known by the name scientific name of Cheirodon axelrodias as well as Hyphessobrycon cardinalis, it eventually adopted its current name—Paracheirodon axelrod.
Species 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.
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 band 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.
Cardinal Tetras, like other Tetra species, are a peaceful fish and they should be kept in schools. Schools should be large, with a minimum size of a half dozen fish. 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 them 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.
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 encompass a broader range, from 73 to 81 F (23 to 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 even 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 an open center space is an ideal habitat for this species.
The Cardinal Tetra is an omnivorous species and will accept most foods. For optimal health, feed them 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.
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.
In home aquaria, breeding Cardinal Tetras is challenging at best. 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. Stock the tank well with fine-leaved plants, as this species will scatter their eggs on the vegetation.
Lighting must be very low and use floating plants to ensure the tank remains dark. Young fry is 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 remove them from the tank once spawning is complete.
In approximately 24 hours the eggs will hatch and live off the yolk sack for another four to five days. Once the fry is free swimming, feed them infusoria, rotifers, egg yolk or commercially prepared fry food. Follow this with freshly hatched brine shrimp as the fry grow.