Black tetra (lat. Gymnocorymbus ternetzi)

Black tetra or black skirt tetra (lat. Gymnocorymbus ternetzi) — is a kind of freshwater fishes of the Characidae family. It inhabits in the rivers of Mato Grosso, Paraguay and Rio-Negro. This kind of fish has easily adapted to aquarium conditions, it breeds easily and has a numerous offspring. However, this fish may start nipping other fishes fins, so it’s not a good idea to keep it in a tank with veiled kinds of fishes or with long-finned ones.

Habitat in the wild

The Gymnocorymbus ternetzi was first described in 1895 by Boulenger, and then it was brought to Europe in 1933.

A model fish species when scientists created glofish tetra.

In the wild habitats are in Mato Grosso, Paraguay and Rio-Negro rivers. However, they have adapted to tank conditions quite well and now the fish is widely spread in aquariums. Tetra prefers slow waters of small rivers, streams, tributaries well shaded by the tree branches.

Nowadays the fish is almost not exported, since the majority of them is bred at farms.


Black skirt tetra has high and flattened body. It grows to be 4.5 cm long and starts breeding just being 4 cm long (1,5 in). Lifespan is about 3-5 years provided with good tank conditions.

The body is laterally flattened, it has dark-silvery coloring with three vertical black stripes.

One of them crosses the eye, the second one starts at the opercles endings. The remaining part of the body starting from the third stripe, including upper and proctal fins, is black and it looks like a skirt.

The pectoral, dorsal and pelvic fins are quite transparent, and its proctal fin reminds a black skirt, as we’ve mentioned earlier. Is rather energetic and active fish, it swims in schools and they often attack each other.

The fish has another color morphs: the long-fin black skirt tetra that was first bred in Europe. It can be very often seen on sale and it has nothing different in care comparing with the classical tetra, but it’s a bit more difficult to be bred due to inbreeding.

As for the albino variation a – they are encountered more seldom, but they differ from the black skirt tetra only in color.

Colored skirt tetra (strawberry and blueberry) – these are artificially colored fishes – this is a modern and very popular trend in aquarium husbandry nowadays.

Fishes are colored manually by injecting dyes directly under the skin.

However, you should buy such fishes sensibly, keeping in mind that chemicals have never made anyone healthier and these fishes lifespan is significantly shorter due to this.

Difficulties in keeping

Care is undemanding and this is a fish for beginner. It adapts well and it eats any kind of feed. The fish is good for community tanks at the condition that it won’t have long-finned tank mates.

Care and keeping in a tank

Scientific NameGymnocorymbus ternetzi
Common NamesBlack tetra, black skirt tetra, skirt tetra, petticoat tetra, widow fish, and black widow tetra, striped tetra, black fin tetra
Tank sizemore then 15 gallons (70L)
TemperamentPeaceful/alone it becomes aggressive
Temperature20–26 °C (68–79 °F)
Length6 cm (2.4 inches)

Since black skirt tetra is a very active one, it has to be kept in spacious tanks from 15 gallons capacity. The fish likes soft and acidic water with fluctuants and not bright light.

Don’t forget to close your tank, because the fish can jump pretty well and it can die outside.

This kind of fish perfectly appears in a tank with natural biotope – sandy bottom, number of snags and fallen leaves on it, which make the tank water brownish and acidic.

Tank maintenance is a standard one and the same as for all other fishes. Weekly water renew up to 25% from the total water amount and a filter are common requirements.

Water parameters may be different, but these are the most preferable ones: temperature 20–26 °C (68–79 °F), ph: 5.8-8.5, 5° to 20° dH.


Skirted tetra is completely not demanding as for the feed, so any kind of live, frozen or artificial feed will do. The fish prefers flakes and other types of feed that stay on the water surface.

Tank mates

Due to its peaceful temperament tetra can be kept in a tank together with other small Characins.

The fish is ideal for mixed aquarium. Fish must be kept in schools, since when it’s all alone it becomes aggressive. It’s better not to keep it together with smaller fishes or long-finned ones.

Because they will bite the latter, for example, don’t keep it with bettas or angelfish. Cardinal tetra, neon tetra , black neon tetra, tiger barb and other not large and active fishes will be good tank mates for that fish.

Gender differences: male vs female

Males have longer and more sharpened fin, at that the female is fatter and the black skirt on its proctal fin is significantly wider.


Is an egg-laying fish and suitable spawning temperature for it is — 25—27 °C, water hardness Dh=4°, pH 6,8-7,0.

Breeding occurs between the fish couples (sometimes it happens in a school). First, male is put into a spawning tank and then it a few hours – the female.

Next day in the morning you should light the tank very brightly – this will push the spawning.

The light may be both natural and artificial. The spawning tank should have its bottom square equal to about 1500 sm² (50×30 см) with some Javan moss or a caproic net put on its bottom.

The net should have its cells wide enough for the falling fish eggs to get through and at the same time – not too large – to prevent fish from eating them.

A couple can lay up to 500 and sometimes 1000 eggs during one spawning. After it is finished the fishes are removed from the spawning tank. The eggs incubation time is 24-36 hours, then larva appear and in 3-5 days they turn into juveniles, start to swim and feed.

The start feed for them is – infusorians and rotifers. Less of the juveniles survive if you feed them with some artificial feed.

Also, while juveniles grow, they should be sorted and put into different tanks according to their size to prevent cannibalism among them.

About author: Sergey Schulz

Sergey is a founder and author of He’s been fond of aquarium husbandry since his early childhood. His favorite aquariums are biotopes (Amazon River), with Echinodorus and freshwater angelfish. However, through the years he’s had experience of keeping almost all types of freshwater fish and shrimps.