Black Widow Tetra (Gymnocorymbus ternetzi) Fish Species Profile

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The Black Widow Tetra is a peaceful, hardy, active and easy to care for fish, they can adapt to a wide variety of different water parameters, making it a popular species to have in an aquarium.

Although they are very peaceful, they may nip at other long-finned species such as Guppies or Betta's so avoid keeping them with those long, flowing fin species.

The Black Widow tetra is easily identified by the distinguishing black anal and dorsal fins, and by the vertical black bars on the body.

Scientific NameGymnocorymbus ternetzi
Other NamesLongfin Black Skirt Tetra, Golden Skirt Tetra, Coloured Skirt Tetra
OriginsSouth America
Aquarium LevelBottom - Middle
Best kept asGroups 5+
Lifespan3 - 5 years
Maximum Sizeup to 7.5 cm
Water Conditions
Water TypeFreshwater
Temperature68 - 78 ℉ (20 - 25.6 ℃)
PH6.0 - 7.0
GH5 - 20
KH10 - 1

Origins of the Black Widow Tetra

Black Widow Tetras inhabit small, slow-moving creeks, tributaries and streams in Rio Paraguay and Guapore basins in Brazil, Bolivia and Argentina in Brazil, South America.

In their habitat, you will usually find them in dense overhanging vegetation that provides them with both shade and food.

They gather near the water's surface where they will eat crustaceans, small worms and insects.


Black widow tetras will accept virtually any food, including granules, flakes and freeze-dried foods.

Regular, small but often feedings of frozen, and small live foods such as Bloodworm and Daphnia are highly recommended as it provides optimal health and colour.

Sexing the Black Widow Tetra

It is quite simple to determine the sex of a Black Widow Tetra.

The females are generally bigger than the males, and their bodies are more rounded. 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 a more pointed dorsal and anal fins.

Breeding the Black Widow Tetra

Black widow tetras are relatively easy to breed.

You will need to set up a separate tank that is dimly lit and contains plenty of fine-leaved plants like Java Moss or dwarf ambulia if these are unavailable spawning mops will also be adequate 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.

For the most success in breeding, you should have slightly acidic water, and the temperature needs to be just a couple of degrees higher than the average temperature and make sure you feed your fish plenty of live and frozen foods.

There are two ways in which you can breed your Black widow tetras, the first being; having a group with several fish of each sex spawning, or selecting a pair of your best fish, an example of this would be your most vibrant colour male and your fattest female.

As soon as eggs are noticed in the aquarium, the adults need to be removed otherwise given the opportunity they will eat them. The eggs will hatch approximately 2 - 3 days, and the fry will become free-swimming a few days after.

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- Updated: 8/4/2020 6:11:31 PM