Black Widow Tetra

Black Widow Tetras sound scary but make good pets

Black widow tetra

emptyvi / Wikimedia Commons / CC BY-SA 3.0

This active, fast-moving species is a great choice for aquarium beginners. Hardy and easy to care for, the Black Widow Tetra (or Black Skirt if you prefer a less scary name) is a schooling fish that comes in several varieties and colors. Buy at least six or seven to create a healthy, happy school of fish, and avoid housing them in the same tank as smaller fish (particularly those with long, flowing fins) as Black Widows do occasionally nip. While the wild Black Widow Tetra is dark in color, you might also want to consider one of the more interesting colored varieties that have been bred in captivity.

Breed Overview

Common Names: Black Tetra, Black Skirt

Scientific Name: Gymnocorymbus ternetzi

Adult Size: 2 inches

Life Expectancy: 5 years


Family Characidae
Origin Rio Paraguay, Rio Guapore, Bolivia
Social Peaceful, good community fish
Tank Level Mid dweller
Minimum Tank Size 10 gallons
Diet Omnivore, eats most foods
Breeding Egg layer
Care Easy
pH 5.8–8.5
Hardness up to 15 dGH
Temperature 68–79 F (20–26 C)

Origin and Distribution

Black Widow Tetras originate from the small, slower tributaries and creeks of the Guapore and Paraguay Rivers in Brazil, where the forest canopy provides both shade and food. They congregate near the surface of the water where they eat insects, crustaceans, and small worms. Originally they were only available as wild-caught, but all specimens sold now are entirely captive-bred, leading to a number of new man-made variations of this popular fish. Additionally, similar species have been described, including Socolof's Tetra (Gymnocorymbus socolofi) and the False Black Tetra (Gymnocorymbus thayeri). Both of these species are not as frequently available in the aquarium trade, nor are they as popular as the Black Widow Tetra.

Colors and Markings

One of the best-known members of the tetra family, the Black Widow Tetra is easily recognized by the distinctive black dorsal and anal fins, and vertical black stripes on its body. A number of varieties with different colors as well as long fins have been produced, some of which are artificially colored. Naturally occurring color variations include white and pinkish-hued varieties. In addition, there are a number of pastel-colored specimens that have been achieved with dyes. Avoid any fish that may have been artificially colored as they are more susceptible to disease. Contrary to some reports, the process of dying is stressful to the fish, and the stress shortens its lifespan. Purchasing these fish only serves to support the practice.

Once the Black Widow Tetra achieves its mature size at approximately one year, the dark coloration slowly begins to fade to a silvery gray. By the time the fish has reached five years or more in age, it is quite pale in color. They also pale when stressed or ill. Black Widow Tetras remain relatively small, reaching an adult length of approximately two inches. Hybrids, such as the long-finned varieties, tend to be a bit larger. Other versions of the Black Widow Tetra include the Longfin Blackskirt Tetra, the Goldenskirt Tetra, and the Colored Skirt Tetra. 


A schooling fish by nature, Black Widow Tetras are best kept in groups of three or more. They make an excellent community fish due to their peaceful nature. Some owners report that they sometimes nip the fins of slower-moving fish, particularly those with long, flowing fins such as Bettas or Angelfish.

Black Widow Tetra Habitat and Care

Black Widows are an undemanding species that adapt to a range of conditions, though subdued lighting and neutral-colored gravel substrate are preferred. They are accustomed to large plants in their natural habitat and enjoy a well-planted aquarium with some open swimming space. Although not demanding about water, they prefer soft acidic water, preferably tannin-stained. Ideally, you should initially match them to the water conditions from the supplier, as sudden changes are not healthy. Cold water can stress Tetras, leaving them vulnerable to a number of diseases such as Ich.

Black Widow Tetra Diet

When at home in nature, Black Widow Tetras eat a lot of live foods. However, they readily accept virtually any food, including live, fresh, frozen, freeze-dried, or flake foods. For the breed's optimal health, provide a variety of foods, which can include high-quality flake foods, brine shrimp, and any type of worms, as well as vegetable supplements such as spirulina.

Sexual Differences

Female Black Widows are generally larger than the males and have a rounder body. In the female, the anal fin runs parallel with the vertical black stripe in her abdomen. Males occasionally have white spots on the caudal fin; they are smaller, have a broader anal fin, and a narrower, more pointed dorsal fin.

Breeding the Black Widow Tetra

Black Widow Tetras do not reach their sexual maturity until nearly 2 years of age. Larger males generally claim a territory that they will guard during their spawning periods. Black Widow Tetras may be spawned in groups having a few more males than females or as pairs. Condition spawning fish, either pairs or groups, with live foods. If you do not have live foods available to you, you can substitute frozen live food. This species prefers to scatter their adhesive eggs among vegetation, so provide plenty of fine-leaved plants such as Java Moss or spawning mops. Keep the water temperature at 78–80 F in a dimly lit tank. Once spawning has occurred, remove the parents as they will quickly consume the eggs.

Eggs will hatch after approximately one day. Feed the fry freshly hatched brine shrimp, egg yolk, or finely ground flake foods.

More Pet Fish Breeds and Further Research

Tetras come in many shapes, sizes, and colors. Some have bright red or blue markings; others have flowing fins. One, the Glowlight Tetra, actually glows in the dark. In addition to their beauty and diversity, Tetras are generally inexpensive and easy to care for. It should be no surprise, then, that Tetras are among the most popular aquarium fish in the world. If you’re interested in similar breeds, check out:

Otherwise, check out all of our other freshwater pet fish breed profiles.