Black Widow Tetra Fish Species Profile

Hardy and easy to care for, the black widow tetra (or black skirt tetra) is a schooling fish that looks great in a medium to large aquarium where a school of them can swim together. While the wild black widow tetra is silver with two dark bands and and the back half of the body is black, there is also a white color variety. The white variety has been modified with bright color genes from jellyfish to create many colors of GloFish that have been captive-bred. There are also longfin varieties of all the color morphs of black widow tetras. 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.

Characteristics

Origin and Distribution

Black widow tetras originate from the small, slower tributaries and creeks of the Guapore and Paraguay Rivers in Brazil, Paraguay, and Argentina, where the forest canopy provides both shade and food. They congregate near the surface of the water to 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 GloFish 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 bands on the body. Color variations produced by selective breeding can be white, golden, or pinkish-hued. But a number of different colored strains produced by genetic modifications, as well as long-finned varieties, have been created.

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 in age, it is usually quite pale in color. These fish also pale when they are stressed or ill. 

Tankmates

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.

While black widow tetras are adaptable, they thrive in soft, acidic water that is often tannin-stained. It's crucial to initially match water conditions to the supplier's to avoid stressing the fish, as sudden changes are intolerable. Cold water can cause stress, making tetras susceptible to diseases like 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 their 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 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 period. 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, hard-boiled 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:

• Cardinal tetra species profile
• Black phantom tetra species profile
• Glowlight tetra species profile

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