The black tetra also known as the black skirt tetra, high-fin black skirt tetra or black widow tetra is a freshwater fish of the characin family (family Characidae) (which includes all tetras, including the piranha), of order Characiformes. It is native to the Paraguay and Guaporé River basins of southern Brazil, Argentina, and Bolivia.
Growing to about 6 cm (2.5 in) total length, the black tetra has a roughly tetragonal body shape and is greyish in colour, fading from light at the nose to near black at the tail. Two prominent black vertical bars appear just posterior of the gills. It is a schooling fish, and requires at least 6 in a group, but they can also make do with 3-4 tetras per aquarium.

The black widow tetra feeds on small crustaceans, insects, and worms.
The white widow tetra reaches sexual maturity at about two years of age. They will spawn in water 78 degrees F. A separate spawning tank, heavily planted and at least 15 gallons, is recommended. Like most characins, white tetras spawn by intermittently releasing and fertilizing eggs among the plants. These fish are frequent egg-eaters and must be removed after spawning. The young are easy to raise, subsisting on newly hatched brine shrimp or powdered processed foods.