Max Size: 7.5cm

Black Widow Tetra (Gymnocorymbus ternetzi)

The Black Widow Tetra, also known as the Black Skirt Tetra (Gymnocorymbus ternetzi), is a peaceful, active and hardy fish that can adapt to various water parameters. They are a popular fish species to have in any aquarium.

Although Black Widow Tetras are generally peaceful, they may display some aggressive behaviour and nip at other species with intricate finnage, so it would be best to avoid keeping these Tetras with Guppies or Siamese Fighting Fish. However, you can usually rectify this behaviour by keeping them in a small shoal of 6 to 8 individuals. Any squabbling can generally be contained within the group when maintained in these numbers.

The ideal tank mates for these fish could include most livebearers, Danios, Rasboras, other Tetras and peaceful bottom dwellers such as Corydoras Catfish.

They would also make suitable companions for Dwarf cichlids such as Kribensis and Angelfish.

Black Widow Tetras are unfussy regarding the decor in their aquarium; however, these Tetras enjoy having an open swimming space as they are pretty active and enjoy having some quieter areas. These Tetras will exhibit their best colours when some areas of dense planting are included in the aquarium. In addition, they will also appreciate floating plants, so the light is subdued.

The Black Widow Tetra is easily identified by their distinguishing black anal and dorsal fins and two prominent vertical black bars on their body posterior to the gills. In addition, these Tetras have a greyish tetragonal body shape that fades from dark at the caudal fin to light at the nose.

The Black Widow Tetra has a reasonably long lifespan, can live anywhere up to 5+ years when properly taken care of, and has plenty of room. It would help if you aimed for a minimum tank size of 10 gallons (45.4 litres) and up, depending on how many Black Widow Tetras you intend to keep and other tank mates you already have or plan to keep in the future.


Longfin Black Widow Tetra
Black Widow Tetra
Black Widow Tetra
Black Widow Tetra
Black Widow Tetra
Black Widow Tetra
Black Widow Tetra
Black Widow Tetra
Black Widow Tetra
Black Widow Tetra
Black Widow Tetra
Longfin Black Widow Tetra
Quick Facts
Scientific NameGymnocorymbus ternetzi
Year Described1895
Other NamesBlack Tetra, Black Skirt Tetra, Petticoat Tetra, Blackamoor
OriginsArgentina, Bolivia, Brazil
Aquarium LevelMiddle - Top
Best kept asGroups 6+
Lifespan3 - 5 years
Water Parameters
Water TypeFreshwater
PH6.0 - 7.0
GH5 - 20
KH10 - 1
68 - 78℉
20 - 25.6℃

Natural Habitat

Paraguay River
Paraná River


In the home aquarium, the Black Widow Tetra will readily accept most good quality dried foods such as granules, flakes and sinking pellets. These modern food products have been developed to provide all adequate nutrition to maintain your fish's health and dietary requirements.

Providing additional foodstuffs such as live, frozen, and freeze-dried meals such as bloodworm, daphnia, and tubifex once or twice a week will provide additional benefits to your fish's health and well-being but is not a must for this fish.

It should be noted that bloodworms should only be given as an occasional treat and should not be used as the staple diet as they are difficult for fish to digest and can potentially cause blockages.

This fish is an omnivore in the wild, meaning it will consume some vegetable matter. Although most modern fish foods take this into account and include them in their products, you can still supplement your fish's diet with blanched vegetables such as spinach, broccoli, and zucchini. Ensure you do not overfeed your fish and remove any leftovers the following day.

Tank Mates

10 interesting tank mate ideas for the Black Widow Tetra could include:

Adolfos Catfish(Corydoras adolfoi)
Black Phantom Tetra(Hyphessobrycon megalopterus)
Denison Barb(Sahyadria denisonii)
Flame Tetra(Hyphessobrycon flammeus)
Glowlight Danio(Celestichthys choprae)
Marbled Hatchetfish(Carnegiella strigata)
Panda Corydoras(Corydoras Panda)
Panda Garra(Garra Flavatra)
Pentazona Barb(Desmopuntius Pentazona)
Red Eye Tetra(Moenkhausia sanctaefilomenae)

Sexual Dimorphism

It is pretty simple to distinguish between the males and the female Black Widow Tetras. Females are typically bigger than males, and their bodies are more rounded. In addition, the female's anal fin runs parallel with the vertical black bar on the stomach, whereas the males tend to have white dots on the caudal fin and more pointed dorsal and anal fins.

The Black Widow Tetra has been featured on the following stamps

Vietnam - 1984

Frequently asked questions

Are Black Widow Tetras schooling fish?

Yes, the Black Widow Tetra is a schooling fish.

How big do Black Widow Tetras get?

The Black Widow Tetra can grow to a maximum size of 7.5cm, with females being larger than the males once they mature.

How long do Black Widow Tetras live?

The typical lifespan of the Black Widow Tetra is between 3 and 5 years. However, how long the Black Widow Tetra will live will depend significantly on how well they are maintained and the quality of their diet.

How many Black Widow Tetras should be kept together?

Like all schooling fish, Black Widow Tetras enjoy the company of other fish of the same species; therefore, you should aim to keep 6 to 8 individuals. The more, the better.

What fish can I keep with the Black Widow Tetra?

The Black Widow Tetra is an ideal and popular community aquarium fish that can be kept with many other fish species. Such as Corydoras, Plecos, more temperant Barbs such as the Denison Barb and other similar tetras also from Brazil, including the Black Phantom Tetra.

More aggressive barbs such as Tiger and Black Ruby Barbs should be avoided, especially with the longfin variant of the Black Widow Tetra.

Other Tetras of interest

Adonis Tetra(Lepidarchus adonis)
African Moon Tetra(Bathyaethiops caudomaculatus)
African Red Eyed Tetra(Arnoldichthys spilopterus)
Arowana Tetra(Gnathocharax steindachneri)
Black Darter Tetra(Poecilocharax weitzmani)
Black Line Tetra(Hyphessobrycon scholzei)
View all Tetras
Date Added: 01/01/2020 11:37:54 - Updated: 08/08/2022 17:50:15