Black Skirt tetra – Gymnocorymbus ternetzi

Black Skirt tetra information:

Scientific name:                 Gymnocorymbus ternetzi 
Common name:                Black Skirt tetra, Black tetra, Skirt tetra
Max. size:                           6.0 cm  / 2.4 inches
pH range:                          6.0 – 8.0
dH range:                           5 – 19
Temperature range:         20 – 26°C (68 – 79°F)

The Black Skirt tetra is a popular aquarium fish. It can be recognized on its characteristic black “skirt”. There exists an albino version of the Black Skirt tetra that is quite common in pet shops and known as the White Skirt tetra. Unfortunately, White Skirt tetras are often dipped in pastel colours and marketed as Fruit tetras. The dying process hurts the fish, and this is not only a problem for the fish itself – it is a problem for the aquarist as well since dyed fish will be highly prone to illness and have a greatly reduced life span. You can however also find White skirt tetras that are pastel coloured because they have been fed coloured food. These tetras are usually healthy, but they will of course loose their colouration if you start giving them normal fish food.

Black skirt tetra

Black skirt tetra picture. Copyright

Black Skirt tetra habitat and range:

The Black Skirt tetra is native to Bolivia, Brazil and northern Argentina and inhabits subtropical river basins where the water temperature stays between 20 and 26° C (68 and 79° F). The Black Skirt tetra was earlier regarded as native to Paraguay too, but this turned out to be a case of mistaken identity. The Black Skirt tetra has today been introduced to nearby Colombia as well as too far away Thailand. The Black Skirt tetra is a pelagic species that will spend its time in the middle and upper water layers.

Black Skirt tetra description:

The Black Skirt tetra can be easily recognized on its characteristic black dorsal and anal fins. The body is decorated with black vertical stripes. The Black Skirt tetra will reach its adult size when it is roughly one year of age, and this is also when the Black Skirt tetra will display its strongest colouration. As the fish grows older, the Black Skirt tetra will become duller and the colouration will fade to a silvery gray shade.

The anal fin of the female Black Skirt tetra is narrower than the male anal fin. The front edge runs parallel with the second vertical line on her abdomen. The dorsal fin is also less pointed in females. In male Black Skirt tetras, the front edge of the anal fin slants back towards the tail. You can also distinguish the two sexes by looking at their body shape; the female is typically plumper than the male. Male Black Skirt tetras will sometimes sport white dots on the caudal fin.

Today, you can purchase a captive bred long-finned Black Skirt tetra variant as well as several colour variations. These genetic colour variations should not be confused with the artificially coloured skirt tetras.

Black Skirt tetra setup and tank mates:

The aquarium where you keep your Black Skirt tetra should be at least 60 centimetres (24 inches) long. Keep at least five Black Skirt tetras together. Black Skirt tetras that are kept alone or in really small groups will typically become shy and much stressed. They will spend most of their time hiding and the stress can weaken their immune system and make them more prone to illness.

Black Skirt tetras are generally peaceful and can be kept in community aquariums with other peaceful fish species of similar size. They can however be a bit nippy when kept with fish that have long and flowing fins, such as Angelfish and Bettas, especially if the Black Skirt tetras are kept in a small group. If your Black Skirt tetras start to nip, you can often solve the problem by purchasing more Black Skirt tetras and create a larger shoal.

Black Skirt tetra care:

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).

The Black Skirt tetras can adapt to a wide range of conditions, but rapid changes and extreme conditions should naturally be avoided. The recommended pH range is 6-8 and the dH should be kept between 5 and 19.

Try to mimic the natural Black Skirt tetra habitat when you set up the aquarium and include a lot of large plants. The Black Skirt tetra will appreciate subdued lighting. The recommended substrate is neutral coloured gravel.

Black Skirt tetra feeding:

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. Healthy Black Skirt tetras are happy eaters in the aquarium and will accept virtually any type of food. Keeping them on a varied diet is recommended. They will eat live and fresh food as well as frozen, freeze dried and flake food. You can use a high quality tropical flake food as a base, and combine it with worms, brine shrimp and spirulina.


Sexing Black skirt Tetras can be tricky, because males and females look quite similar. The female does however display a rounder belly and normally grows bigger than the male. During the breeding period, both sexes tend to darken their color. Black Tetras kept in a suitable environment and given nutritious food will also display darker colors than other Black Tetras. If you want to breed Black Tetras, the best method is to keep a school together and let them form their own pairs. This way, you do not have to try sexing them. After all, this is a schooling species, and keeping them in pairs is never really a good idea.

Breeding Black skirt Tetras

Getting Black skirt Tetras to spawn is not difficult, the tricky part is to keep eggs and fry from being eaten by adult fish. To get them to spawn, a planted 10-20 gallon aquarium is usually enough. Keep the water quality up, feed your fish nutritious food, and keep the water temperature around 26-27 degrees C. The pH-value should be around neutral and the water hardiness below dH 15 (the lower the better). Adding spawning grass to the bottom is appreciated but not mandatory.

As mentioned above, adult fish can eat eggs and fry and should therefore be removed from the aquarium. If your fish gets really stressed when you catch them, you can instead hang a large net or basket inside the aquarium and place the adult fish in it before they spawn. This way, the eggs will fall down through the mesh and rest safely at the bottom. This method is also a great alternative if you only have one aquarium.

Black Tetra eggs

The Black skirt Tetra is an egg scattering species that produces large quantities of really small eggs. Unfertilized eggs will soon start to look fuzzy due to fungi growth and should be removed from the aquarium to prevent the fungi from attacking healthy, fertilized eggs. The eggs normally hatch within four days at 26 degrees C.

Caring for the fry

Newly hatched Black skirt Tetra fry are really minute and will spend most of their time clinging to walls and aquarium decoration. You can feed them liquid fry food, micro worms or vinegar eels. When they are around three days old, they will be large enough to eat newly hatched brine shrimp. One month old Black Tetra fry can be given the same food as their parents.

Large water changes are harmful to Black Tetra fry and you should therefore only change a small amount of water each time. Preferably carry out small water changes several times a day to keep the water quality up without casing any rapid changes.