Cardinal tetras are peaceful schooling fish suited for community tanks, requiring a group of at least six to maintain their social structures.
They thrive in established tanks with soft, acidic water (pH below 6), subdued lighting, and a stable temperature between 73 to 81 F (23 to 27 C).
Cardinal tetras are similar in appearance to neon tetras but can be distinguished by a red stripe that runs the full length of their bodies, whereas, in neon tetras, it extends only from mid-body to tail.
Cardinal Tetra
Tankmates
Cardinal tetras, like other tetra species, are peaceful, social fish that 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.
Potential tank mates that may be suitable include:
- Other tetra species, such as the flame tetra and glowlight tetra
- Danios
- Rasboras, such as the harlequin rasbora and scissortail rasbora
- Dwarf gouramis
- Small members of the catfish family, especially Corydoras catfish
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.
Cardinal Tetra Habitat and Care
Much like the neon tetra, this species requires a mature tank that has soft, acidic water. More importantly, water chemistry should be stable. This is not a species that does well in a newly started aquarium.
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).
Lighting should be subdued, as should the décor. Floating plants are a good means for moderating the lighting. Although they require some hiding spaces, it is important to provide cardinal tetras with open-water swimming area as well. A well-planted tank with an open center space is an ideal habitat for this species.
Cardinal Tetra Diet and Feeding
The cardinal tetra is an omnivorous species and will accept most commercial fish foods. These fish have high vitamin requirements, so at least 75% of their food should be quality flake food. Cardinal tetras especially appreciate live and frozen foods, but if fed them exclusively they may reject prepared food later on.
If only doing one to two feedings a day, offer what they can eat in about five minutes. However, it is better to feed these fish several times a day, offering only what they can eat in about three minutes. All foods should be in small pieces, as cardinals have a small mouth. When conditioning breeders, live foods are important.
Gender Differences
Males and females show few clear differences between the genders. Females will have a somewhat deeper body with a rounder belly, while males are more slender. Males also have a hook protruding from the anal fin.
Breeding the Cardinal Tetra
Breeding cardinal tetras is challenging at best. A separate breeding tank is important, and it must have stable water chemistry: a pH of 5.0 to 6.0 and very soft water of 3 to 5 dGH or below are essential. They will spawn in the evening, generally laying between 130 and 500 eggs. Spawning will continue even late into the night hours.
In approximately 24 hours, the eggs hatch, and the fry live off of their yolk sac for another four to five days. Once the fry are free swimming, feed them infusoria, rotifers, hardboiled egg yolk, or commercially prepared fry food. Follow this with freshly hatched brine shrimp as the fry grow. Lighting must be kept very low; use floating plants to ensure the tank remains dark. The young tetra fry are highly photosensitive.
This species reaches a mature size of up to 2 inches in home aquaria.