Swordtail Tetra

Swordtail Tetra, Corynopoma riisei, is a South American characin native to northern Venezuela, Trinidad, and parts of northeastern Colombia. It inhabits slow-moving streams, floodplain waters, ponds, and vegetated backwaters where water is warm, moderately soft, and rich in aquatic vegetation. These habitats often contain dense marginal cover and open areas where schools can move freely.

Adult Swordtail Tetras typically reach about 2.5 to 3 inches in length. The body is slender and silvery with subtle iridescent blue, green, and gold reflections that become especially noticeable under aquarium lighting. The species is best known for its remarkable sexual dimorphism. Males develop elongated extensions on the caudal fin that resemble miniature swords, along with modified scales and fin structures used during courtship displays. Females are larger-bodied and lack the dramatic fin extensions but still display attractive metallic coloration.

A tank of at least 20 to 30 gallons is recommended for a proper group. Swordtail Tetras are active schooling fish and should be maintained in groups of six or more. The aquarium should provide open swimming space along with plants, driftwood, and shaded areas around the perimeter. Dense vegetation helps females avoid excessive attention from displaying males while creating a more natural environment.

Water conditions should remain stable and clean. Temperatures between 74 and 82 degrees Fahrenheit are appropriate, with a pH range of roughly 6.5 to 7.8 and soft to moderately hard water. This species is relatively adaptable but thrives best in well-maintained aquariums with regular water changes and good filtration.

Feeding is straightforward. In nature they consume insects, small crustaceans, and other aquatic invertebrates. In the aquarium they readily accept flakes, micro-pellets, frozen foods such as daphnia, brine shrimp, bloodworms, and other prepared foods. A varied diet helps maintain condition and supports natural breeding behavior.

Temperament is peaceful and community-friendly. Swordtail Tetras do well with other small to medium-sized non-aggressive fish including tetras, rasboras, Corydoras, dwarf cichlids, and peaceful livebearers. Males spend much of their time displaying to females and one another, but serious aggression is uncommon.

Breeding is possible in captivity and is one of the most fascinating aspects of the species. Males perform elaborate courtship displays using their elongated caudal extensions and specialized scent-producing structures to attract females. Eggs are scattered among plants, and adults provide no parental care.

Corynopoma riisei is a unique and highly underrated tetra that combines metallic coloration with some of the most unusual courtship behavior found among freshwater fish. Its distinctive sword-like tail extensions and active social displays make the Swordtail Tetra an outstanding centerpiece species for planted community aquariums.