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.

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Natural Habitat

Feeding

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:

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.