Saturday, June 21, 2008

Black Widow Tetra

Data Sheet

Scientific Name: Gymnocorymbus ternetzi
Other Names: Black Tetra, Black Skirt Tetra
Adult Size:2.5 inches (6 cm)
Lifespan:5 years
Tank Level: Mid Dweller
Minimum Tank Size:10 gallons
Diet: Omnivore
Breeding:Egg Layer
Ideal pH: 6-8
Temperature: 68-78 F (20-26 C)
Tank setup: Ideally planted aquarium
Females are generally larger and have rounder body.


Growing to about 6 cm (2.5 in) total length, the black window tetra has a roughly tetragonal body shape and is greyish in colour, fading from light at the nose to near black at the tail. Two prominent black vertical bars appear just posterior of the gills.


The Black Skirt tetra is a very hardy fish that is suitable for beginner aquarists. Since it is native to subtropical waters, it will appreciate a lower temperature than what is found in most tropical aquariums. Ideally keep the temperature between 20 and 26° C (68 and 79° F).

A schooling fish by nature, black widows Tetra are best kept in groups of six or more. Due to their peaceful nature, they make an excellent community fish. FishLore noted that Black Widow Tetra sometimes nip the fins of slower moving fish, particularly those with long flowing fins such as Bettas Angelfish. However, when keep in groups of 6 of more, they tend to chase one another harmlessly and leave the other fishes alone. or

The Black Skirt tetras can adapt to a wide range of conditions, but rapid changes and extreme conditions should naturally be avoided. The aquarium should ideally include a lot of large plants.


The black widow tetra is an omnivore and will eat nearly anything it can fit into its mouth. Wild Black Skirt tetras are mainly carnivores and feed on insects, worms and small crustaceans. They do however also ingest smaller amounts of algae and plant matter. In an aquarium, it cheerfully and readily accept flake food, worms, and brine shrimp.


To breed the black widow tetra in captivity, the aquarium should ideally be densely planted with fine-leaved plants as the Black Skirt tetra is an egg-scattering species that prefers to release the eggs among fine-leave plants. The male will claim a territory during the breeding period and defend it.

Once the eggs are laid, the parents should be removed from the tank as these fishes tend to eat their own eggs. The eggs will typically hatch within 24 hours. The frys could be feed with egg yolk or newly hatched brine shrimp. As the fry grows larger, you can give them larger and larger brine shrimp.


Black Widow Tetra are prone to WHITE SPOT (Ich, ichthyophthirius). This disease is caused by environmental stress and/or cold water. It can also be caused by sudden changes in water temperature. It is a parasite resembling a grain of salt that feeds on the tissue of the fish causing irritation. It spreads through the skin and fins and will eventually kill the fish if left untreated. The mature parasite cannot be killed, nor can its eggs. It can only be destroyed in its free swimming stage after the spot falls off and the eggs hatch. This can take from 1-4 days. This is why it is important to continue to medicate for at least 3-5 days after the spots are gone. Add 1-2 drops of formalin or copper sulfate to the tank water and raise the temperature to 82 degrees (use formalin with great care as it is a cancer causing agent).

References Cited:

1. Black Widow, [Online], Accessed on 12 June 2008 [Available]

2.Black Skirt Tetra [Online], Accessed on 18 June 2008,[Available],

3. Aquatic Community [Online], Accessed on 18 June 2008,[Available],

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