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Maximum size : 7.5 cm

Black Widow Tetra - Gymnocorymbus ternetzi : Complete Fish Profile & Care Guide

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The Stunning Black Widow Tetra, also known as the Black Skirt Tetra (Gymnocorymbus ternetzi), is a versatile, active, and hardy fish that can adapt to a range of water parameters, making it a popular choice for many aquarium enthusiasts. While generally peaceful, Black Widow Tetras may occasionally exhibit aggressive behavior and nip at other species with intricate finnage. To minimize this issue, avoid housing these Tetras with Guppies or Siamese Fighting Fish. Keeping them in a small shoal of 6 to 8 individuals can help contain any squabbles within the group. Ideal tank mates for Black Widow Tetras include most livebearers, Danios, Rasboras, other Tetras, and peaceful bottom dwellers such as Corydoras Catfish. They also make suitable companions for Dwarf Cichlids like Kribensis and Angelfish. Though not particular about their aquarium decor, Black Widow Tetras appreciate open swimming spaces and quieter areas. They display their most vibrant colors when provided with dense plantings and subdued light from floating plants. Easily recognizable by their distinct black anal and dorsal fins and two prominent vertical black bars behind their gills, Black Widow Tetras have a greyish tetragonal body shape that fades from dark at the caudal fin to light at the nose.

Black Widow Tetra Photos

Sexual Dimorphism

Distinguishing between male and female Black Widow Tetras is relatively straightforward. Females are generally larger than males and exhibit a more rounded body shape. Additionally, the female's anal fin aligns parallel with the vertical black bar on the abdomen. In contrast, males often display white dots on the caudal fin and possess more pointed dorsal and anal fins. These differences in physical characteristics make it feasible for aquarists to accurately identify the gender of Black Widow Tetras.
Featured Male
Featured Female
Male Female

Quick Facts

Scientific NameGymnocorymbus ternetzi
Year Described1895
Other NamesBlack Tetra, Black Skirt Tetra, Petticoat Tetra, Blackamoor
OriginsBrazil Bolivia Argentina
Max Size7.5 cm
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

The Black Widow Tetra has been featured on the following stamps.

Natural habitat

The Black Widow Tetras call the Rio Paraguay and Rio Guapore Basins in Brazil, Bolivia, and Argentina their home. These fish are native to small, slow-moving tributaries found in creeks and streams, and they're known to inhabit habitats filled with lush overhanging vegetation. The Black Widow Tetra's preferred environment is not just for show - it provides them with shade and a bounty of food. You'll often find these striking fish gathering near the water's surface, where they showcase their stunning colours and captivating movements. So, if you're seeking an exotic addition to your aquarium, look no further than the Black Widow Tetra - a true gem of South America's waterways.
 Paraguay River - Brazil
Brazil Flag
 Paraná River - Brazil
Brazil Flag

How to breed the Black Widow Tetra

Breeding Black Widow Tetras is relatively straightforward, but it does require the setup of a separate, dimly lit breeding tank with an abundance of fine-leaved plants, such as Java Moss, or spawning mops. Alternatively, a mesh can be used at the bottom of the tank, with holes large enough for eggs to fall through but small enough to prevent adult fish from reaching them. Ensure the breeding tank has slightly acidic water, and the temperature is a few degrees higher than average. Providing ample live and frozen foods is also crucial. Two breeding approaches can be employed for Black Widow Tetras: establishing a group with multiple fish of each sex or selecting a pair, such as the most vibrant male and the plumpest female. Once eggs are detected in the aquarium, promptly remove the adult fish to prevent them from consuming the eggs. The eggs typically hatch within 2 to 3 days, and the fry become free-swimming shortly thereafter. Initially, feed the fry infusoria-type food, transitioning to microworms or newly hatched brine shrimp as they grow larger. Keep in mind that the eggs and fry are sensitive to light during their early stages of life, so maintaining a dim environment is essential.

Diet & feeding

Black Widow Tetras are not particularly demanding when it comes to their diet; however, providing a well-balanced and varied diet is essential for maintaining their overall health and vibrant coloration. Ensure that you offer high-quality dried foods, such as granules and flakes, in addition to live, frozen, and freeze-dried foods like Bloodworms and Daphnia. By catering to their nutritional needs, you will promote the optimal well-being and appearance of your Black Widow Tetras.

Frequently asked questions

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.

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

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

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.

Yes, the Black Widow Tetra is a schooling fish.

10 tank mate ideas for the Black Widow Tetra

Looking for some awesome tank mate ideas for your Black Widow Tetra? Look no further! Here are 10 of the most captivating and fascinating options that will liven up your aquarium!

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