The black tetra is a freshwater fish native to Paraguay and is usually found in the upper layers of basins. It is a popular fish for tropical aquariums. The are small fish, typically only growing to about 2.5 inches (6 cm) in length, and are often seen in groups of five or more.
At birth the black tetra is a dark black color, but as it ages the blackness fades into a duller gray, with a pair of dark vertical stripes complimenting its light color. The dorsal and anal fins of the black tetra are large in comparison to its body. These large fins give the appearance of a "skirt" on the fish, which is why many refer to the fish as a black skirt tetra.
Another common name for the tetra is the black widow tetra, most likely due in part to its somewhat aggressive nature. While the fish should be kept in schools of three or more, it has been known to attack and nip at the smaller members of its school, which can cause stress and shorten fish lifespans. The fish is not known to be aggressive to other fish though, and can be kept in community tanks with other peaceful fish. In nature the fish is carnivorous and eats on small worms, but in a tank it can eat most common fish food, including flakes and frozen brine shrimp.
The black tetra can survive a wide variety of water conditions, making the species a popular choice for tropical aquarium enthusiasts. Many fish experts recommend the black tetra as a starter fish for anyone new to keeping fish as pets. It has a strong tolerance for pH variations, anywhere between 5.8 and 8.5 is acceptable, and can thrive in water that is kept between 70 to 80 degrees Fahrenheit (21 to 27 degrees Celsius). Since it should be kept in schools, this fish should not be kept in a tank smaller than 20 gallons. In a well-maintained aquarium a black tetra can live approximately five years.
Breeding black tetras can be difficult, and is best accomplished in a separate aquarium that is kept solely for breeding purposes. Once the eggs are laid the parents need to be removed immediately. Like most fish, the tetra is not particularly parental in nature, and will eat the its eggs if given the chance. If breeding is successful and the parents removed the eggs will hatch within days.