Black Skirt Tetra

Gymnocorymbus ternetzi

Also sold as Black widow tetra · GloFish tetra

Synonyms Black tetra

Black Skirt Tetra (Gymnocorymbus ternetzi) is a peaceful freshwater fish that reaches about 6 cm (2.4 in) and swims along the bottom in a shoal. It wants 68–79°F (20–26°C) and pH 6–7, is kept in groups of 12 or more, and needs a tank of at least 68 L (18 gal).

At a glance

Type	Fish
Adult size	6 cm (2.4 in)
Minimum tank	68 L (18 gal)
Group size	12 or more
Temperature	68–79°F (20–26°C)
pH	6–7
Temperament	Peaceful
Lifespan	3–5 years
Eats shrimp	Yes

Before it goes in

Black Skirt Tetra needs at least 68 L (18 gal). The smallest size in this library that clears that is the 20 Gallon High.
Keep 12 or more. Below that it hides, colours down and is far more likely to be picked on.
It eats shrimp. Cherry Shrimp, Crystal Red Shrimp and Bamboo Shrimp are on the menu.
It holds at 68–79°F (20–26°C). That shares a window with Betta and Cherry Shrimp, but not with Discus.
It nips fins, so long-finned fish are a bad match.
A group of 12 takes up roughly 133% of what a 20 Gallon High will comfortably hold, so plan the rest of the stock around it.

What tank size does it need?

At least 68 L (18 gal). The smallest size here that clears it is the 20 Gallon High.

How many should I keep?

12 or more. Fewer than that and it spends its time hiding instead of out in the open.

Will it eat shrimp?

Yes. Shrimp are food to it, so pick one or the other.

What water does it want?

68–79°F (20–26°C), pH 6–7.

How long does it live?

3–5 years in a tank that suits it. That is how long you are signing up for.

Good tank mates

Tank mates from this library that share its temperature window, are peaceful and eat neither it nor its young: Goldfish, Bristlenose Pleco, Celestial Pearl Danio, Molly and Otocinclus.
Plants that hold up with it: Hygrophila corymbosa 'Siamensis', Water Sprite, Anubias nana 'Petite' and Cryptocoryne wendtii.

Often compared with

	Black Skirt Tetra	Bleeding Heart Tetra	Buenos Aires Tetra
Adult size	6 cm	6 cm	6 cm
Min tank	68 L	81 L	81 L
Group	12+	8+	8+
Temperature	68–79°F (20–26°C)	70–82°F (21–28°C)	61–82°F (16–28°C)
Eats shrimp	Yes	—	Yes

More livestock

Plan a tank with Black Skirt Tetra →

Sources (4) · checked Sep 2026