Black Widow Tetra Fish Species Profile

Characteristics, Origin, and Helpful Information for Hobbyists

Black widow tetra

emptyvi / Wikimedia Commons / CC BY-SA 3.0

Hardy and easy to care for, the black widow tetra (or black skirt tetra) is a schooling fish that, contrary to its name, comes in several colors. While the wild black widow tetra is dark in color, consider the many-colored varieties that have been captive-bred. At least six or seven specimens create a healthy, happy school of fish, but avoid housing them with smaller species (particularly those with long, flowing fins) as black widows do sometimes nip. This active, fast-moving species is a great choice for aquarium beginners.

Species 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 to 8.5
Hardness up to 15 dGH
Temperature 68 to 79 F (20 to 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.

Other variants of the black widow tetra include the longfin blackskirt tetra, the goldenskirt tetra, and the colored skirt tetra. Additionally, similar species have often been mistaken for this fish, 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 by the vertical black stripes on the body. Naturally occurring color variations can be white to pinkish-hued. But a number of different colored strains, as well as long-finned varieties, have been produced by captive breeding.

Don't be fooled by any number of pastel-colored specimens; these fish have been achieved with dyes. Avoid any individuals that may have been artificially colored as they are much more susceptible to disease. Contrary to some reports, the process of dying is stressful to the fish, and this stress shortens its lifespan a great deal. Purchasing these fish only serves to support this unethical and harmful practice.

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. Once the black widow tetra achieves its mature size at approximately one year, its normal dark coloration will slowly begin to fade into a silvery gray. By the time the fish has reached five years or more in age, it is usually quite pale in color. These fish also pale when they are stressed or ill. 


A schooling fish by nature, black widow tetras are best kept in groups of six 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 substrates 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 tolerated by this species. Colder water can stress tetras, leaving them quite vulnerable to a number of diseases such as Ich.

Black Widow Tetra Diet and Feeding

Black widow tetras 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 and spirulina.

Gender 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 on the 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 may be spawned in groups that have a few more males than females; they may also be spawned as pairs. Condition all spawning fish, either the 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 to 80 degrees Fahrenheit in a dimly lit tank.

Larger males generally claim a territory that they will guard during their spawning periods. 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. Black widow tetras do not reach their sexual maturity until nearly two years of age.

More Pet Fish Species and Further Research

In addition to their beauty and diversity, tetras are generally inexpensive and easy to care for. Hence, the tetras are among the most popular aquarium fish in the world. If you’re interested in similar species, check out:

Check out additional fish species profiles for more information on other freshwater fish.