Gymnocorymbus ternetzi – Black Tetra

Gymnocorymbus ternetzi or Black Tetra is a nice school fish that is easy to keep in a community aquarium. Keep them in a group of at least six or more!

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Gymnocorymbus ternetzi – Black Tetra

Gymnocorymbus ternetzi is also called Black Tetra. This species has also been scientifically described as Tetragonopterus ternetzi, but this name is no longer valid.

They were first described in 1895 by G.A. Boulenger.


They are peaceful schooling fish that should be kept in a group of at least 6 but preferably more. A Black Tetra kept alone often exhibits deviant behaviour in which it can behave aggressively towards its tank mates.

The Black Tetra is a round-shaped fish with a long fin under its belly. This fin and the dorsal fin are usually black. The fish itself is silver in colour. The belly is slightly whiter. A purplish glow can appear on the entire fish. Striking are the two black transverse bands across the side of the body.

Males are somewhat smaller and slimmer than the females, the dorsal fin is also narrower in the males. At a young age, these fish are at their best with a deep black mark. Depending on the quality of the food offered and the water composition, the markings become greyer as they age.

Gymnocorymbus ternetzi is very suitable for beginners. They make little demands on the water and the decoration. Because it is a very peaceful schooling fish, you can keep it together with almost all other fish. It is a schooling fish so keep them with at least six, but preferably much more. Don’t forget sufficient swimming space!


South America; Argentina, Bolivia and Brazil.


In terms of food, the Black Tetra is not very picky. You can feed them with live food, frozen food. You can also give them dry food, they do not always eat this immediately because they have to get used to it. A variation of dried and living food, flakes, granules is best as this will have all ingredients to keep them healthy.

The aquarium

Gymnocorymbus ternetzi make little demands on the aquarium or water, as long as there is sufficient open swimming space with some plants on the edge. They don’t like very bright lighting. Dimm the lighting with some floating plants and a dark substrate. They certainly appreciate this. They also like a little current.

You can keep the Black Tetra in water with a temperature between 20 and 26 degrees Celsius with a pH of around 7 to 7.5.

In nature, fish have to deal with fluctuating temperatures. Keeping fish at the minimum or maximum temperature for a long time is not always desirable and can shorten the average life of the animals.

Breeding Gymnocorymbus ternetzi

Breeding Gymnocorymbus ternetzi is relatively easy. To get them into spawning, you set the temperature at 25 to 26 degrees Celsius. Plant the aquarium with fine-leaved plants such as Java moss between which the eggs can be deposited. The eggs are laid early in the morning. After spawning, the parents should be removed. Just like most other egg-scattering species, the parents eat their own eggs. After a day the eggs hatch and a day later the young are swimming around freely. In the beginning, you can feed them with some dust food, later also with freshly hatched brine shrimp and egg yolks.



Rickpad – J. de Lange

Copyright images

J. de Lange

Additional information






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