Gymnocorymbus ternetzi

Common Names: Black skirt tetra, black tetra, black widow tetra, white skirt tetra, blueberry tetra, strawberry tetra, mixed berry tetra

Type Locality: Descalvados, Mato Grosso, Brazil

Range: Paraguay and GuaporÉ River drainages in South America

Taxonomic Troubles: Originally described as Tetragonopterus ternetzi

Size: 6 cm TL (2.5 inches)

Preferred Water Chemistry: Subtropical, 20° to 26°C (68° to 78°F), wide range of hardness and pH.

Difficulty: An extremely hardy and adaptable species, recommended for beginners.

Tank Setup: This is an active, schooling species that should always be kept in groups. It should have plenty of open swimming space but appreciates plant thickets to which it can retire if it feels threatened.

Feeding: A micropredator. Relishes live or frozen foods, will readily take all regular aquarium fare.

Breeding: An easily bred egg scatterer. Parents are voracious predators on eggs and fry.

Fish Description

Unique in shape and coloration, this tetra is immediately identifiable with its prominent, curved anal fin and half-black pattern. The tail end of this fish is black, including the dorsal and anal fins. Two partial vertical black bars accent the silvery front portion. The black coloration is quite variable, and it can fade or darken depending on the fish's mood. Domesticated color and fin morphs have been established.


This fish is a perennial favorite, a constant staple for more than half a century. As with any such fish, numerous varieties have been bred and established, including long-fin, pale, and completely white strains (known as white skirt tetras). These white fish are sometimes subjected to dyeing, which creates the various "berry" tetras; this practice should be condemned, as it requires removing the fish's slime coat with acids, followed by immersion in the dye. Aside from the fact that the color fades with time and the fact that it subjects the fish to unnecessary distress, the colors produced pale next to the vibrant natural coloration of so many other species. So why promote the practice?

The black tetra is a peaceful candidate for community tanks, but it may be a bit nippy toward slow-moving or long-finned tankmates. When kept in groups, as it should be, the fishes' energy is usually contained within the group, where it remains harmless. While its color scheme is basic black and white, its pattern and manner provide dynamic interest and contrast to more colorful species. It is especially dramatic when kept in large schools of a dozen or more fish.