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, making them a popular fish species to have in any aquarium.

Although Black Widow Tetras are normally 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 when it comes to the decor in their aquarium; however, these Tetras do 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 is 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.

Tank Mates for the Black Widow Tetra

10 ideal tank mate ideas for the Black Widow Tetra 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)
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℃

Photos of the Black Widow Tetra

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

Natural Habitat

Black Widow Tetras are endemic to the Rio Paraguay and the Rio Guapore Basins in Brazil, Bolivia and Argentina in South America. They inhabit small, slow-moving tributaries in creeks and streams. Their habitats usually consist of dense overhanging vegetation that provides them with both shade and food, and you will find them gathering near the water's surface.

Paraguay River
Paraná River

What to feed the Black Widow Tetra

Black widow Tetras are unfussy when it comes to what they eat; however, make sure you provide them with a balanced diet including good quality dried food such as granules and flakes as well as live, frozen and freeze-dried foods such as Bloodworm and Daphnia. Offering and varied diet will keep your fish in optimal health and colour.

How to sex the Black Widow Tetra

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.

How to breed the Black Widow Tetra

Black Widow Tetras are relatively easy to breed. However, you will need to set up a separate breeding tank that is dimly lit and contains plenty of fine-leaved plants like Java Moss. If these mediums are unavailable, spawning mops will also be fine to use. Alternatively, you can use a mesh on the bottom of the tank, making sure the holes are big enough for the eggs to fall through it and small enough that the adults can not get through it to reach them.

The water in the breeding tank needs to be slightly acidic, and the temperature should be a couple of degrees higher than the average temperature. You should also make sure you provide your fish with plenty of live and frozen foods.

There are two ways in which you can breed your Black Widow Tetras. You can either have a group with several fish of each sex, or you can select a pair of your best fish; an example of this would be your most vibrantly coloured male and your plumpest female.

As soon as you spot any eggs in the aquarium, you will need to remove the adults; otherwise, they will eat them given the opportunity. The eggs will hatch in around 2 to 3 days, and the fry will become free-swimming a few days after that.

It would be best if you fed the fry on infusoria-type food for the first few days, moving on to microworm or newly hatched brine shrimp once they are large enough to accept them. The eggs and the fry are sensitive to light in the early stages of life; therefore, you should keep the tank as dim as possible.

The Black Widow Tetra has been featured on the following stamps

Vietnam - 1984

Frquently asked questions about the Black Widow Tetra

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

African Moon Tetra(Bathyaethiops caudomaculatus)
African Red Eyed Tetra(Arnoldichthys spilopterus)
Black Darter Tetra(Poecilocharax weitzmani)
Black Line Tetra(Hyphessobrycon scholzei)
Black Neon Tetra(Hyphessobrycon herbertaxelrodi)
Black Phantom Tetra(Hyphessobrycon megalopterus)
View all Tetras
Date Added: 01/01/2020 11:37:54 - Updated: 22/04/2022 14:27:24