Black Skirt Tetra

Black Skirt Tetra, Gymnocorymbus ternetzi, is a South American characin native to the Paraguay and Paraná river systems in Brazil, Paraguay, and Bolivia. It inhabits slow-moving rivers, tributaries, and floodplain waters with submerged vegetation, roots, and open swimming areas. These environments are typically warm, moderately soft, and slightly acidic to neutral, with gentle flow and variable water clarity.

Adult Black Skirt Tetras typically reach about 2 to 2.5 inches in length. The body is tall and laterally compressed with a distinctive “skirted” appearance created by the extended anal fin. Coloration is silver to gray with two prominent vertical black bands behind the gill plate and a darker shading through the rear half of the body. The fins are translucent to smoky black, giving the fish its common name. Their shape and contrasting pattern make them easily recognizable in community aquariums.

A tank of at least 20 gallons is recommended for a proper group. Black Skirt Tetras are schooling fish and should be kept in groups of six or more to reduce stress and limit fin-nipping behavior. The aquarium should provide open swimming space along with plants, driftwood, or other structure along the edges for cover. Moderate water movement is appropriate.

Water conditions should be stable and clean. Temperatures between 72 and 80 degrees Fahrenheit are suitable, with a pH range of roughly 6.0 to 7.5 and soft to moderately hard water. This species is adaptable but benefits from regular water changes and good filtration.

Feeding Black Skirt Tetras is straightforward. In nature they feed on small insects, larvae, and plant material. In the aquarium they readily accept flakes, pellets, and frozen foods such as bloodworms, brine shrimp, and daphnia. A varied diet supports overall health and coloration.

Temperament is generally peaceful but can become nippy, especially when kept in too small of a group. They are best kept with similarly sized, active fish that can tolerate occasional fin-nipping. Very slow-moving or long-finned species should be avoided. In proper groups, this behavior is usually reduced.

Breeding is possible in captivity. They are egg scatterers that release eggs among plants or fine substrate. Adults do not provide parental care and may eat eggs if left in the breeding tank.

Gymnocorymbus ternetzi is a hardy and widely kept community fish that offers bold contrast and active schooling behavior. When maintained in proper groups with stable water conditions, the Black Skirt Tetra is a reliable and visually appealing addition to freshwater aquariums.