Black Widow Tetra Fish Species Profile – 10 Important things you must Know

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Characteristics, Origin, and Helpful Information for Hobbyists

Black widow tetra

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



OriginRio Paraguay, Rio Guapore, Bolivia
SocialPeaceful, good community fish
Tank LevelMid dweller
Minimum Tank Size10 gallons
DietOmnivore, eats most foods
BreedingEgg layer
pH5.8 to 8.5
Hardnessup to 15 dGH
Temperature68 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. 


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.Flake Fish Foods and How to Choose the Right Combination for Fish

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.

Black Widow Tetra (Gymnocorymbus ternetzi)

Black Widow Tetra Tropical Fish Learn all about the Black Widow Tetra’s feeding habits and food types, its behaviour, its origins, its natural habitats, is it male or female, breeding advice and information, suitable tank mates, its sizing and growth range, minimum tank size, water PH and more. Use our fish community creator tool to plan your tank set up and ensure that the Black Widow Tetra is the right fish for your aquarium.

The Black Widow Tetra is a peaceful shoaling fish, which is very hardy and suited to a wide range of water conditions. After around a year, the black colour begins to fade to a washed out grey appearance and the fish no longer shoals, preferring its own space. Although very peaceful, the Black Widow Tetra will nip at long finned fish such as Guppies or Siamese Fighting Fish. Keep in aquariums with some hiding spots amongst plants. A good aquarium fish.

Black Widow Tetra Facts

Family Characidae (Characins) | Synonyms Tetragonopterus ternetzi, Gymnocothymbus ternetzii | Other names Black tetra, butterfly tetra | Origin South America; Paraguay and Guapore River basins | Breeding Egg scatterer | Natural Water Conditions pH 6-8, very soft to medium | Sexing Males dorsal fin is pointed and narrow whilst the anal fin is broader.

Black Widow Tetra Help and Advice

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