Black tetra, skirt tetra (Gymnocorymbus ternetzi) care guide

Group
Freshwater fish
Other names
Black widow tetra, Black tetra, Butterfly tetra, White skirt tetra (leucistic form), Long-fin black skirt, Petticoat tetra, High-fin black skirt tetra, Blackamoor
Family
Acestrorhamphidae (American tetras; formerly Characidae)
Origin
South America: the Rio Paraguay and Rio Guaporé basins in Brazil, Bolivia and Argentina. All fish in the trade are captive-bred.
Water
freshwater
Maximum size
6 cm
Temperature
20–26°C
pH
6–7.5
Hardness
Soft to hard, 5–20 dGH
Minimum tank
68 litres
Care level
beginner
Temperament
peaceful
Lifespan
3–5 years years

Care

A tough, active tetra that has been a shop favourite for decades. The deep black of young fish fades to grey as they get older, which is normal. Keep them in a decent shoal: Seriously Fish suggests at least 12 if you want to keep their fin-nipping habit in check, as smaller groups take it out on tankmates. A tank with a base of at least 75 × 30 cm (around 68 litres) suits a small group, and bigger is better for a full shoal. Give them open swimming space alongside some planted areas, and fairly subdued lighting. They cope with a wide range of conditions: temperatures of 20–26 °C, slightly acidic to around neutral water (pH 6–7.5) and soft to fairly hard water are all fine. Avoid artificially dyed or injected fish, which have been offered in the trade: the process is very stressful and often shortens their lives considerably. Selectively bred long-finned and white (leucistic) forms are a different matter and are perfectly normal fish. It is the fish behind the genetically modified fluorescent 'GloFish' tetras, which are not approved for sale in the UK or EU. Sources: Seriously Fish (seriouslyfish.com/species/gymnocorymbus-ternetzi/); FishBase (fishbase.se/summary/Gymnocorymbus-ternetzi.html); Wikipedia (en.wikipedia.org/wiki/Blacktetra). Checked October 2026.

Diet

Omnivorous and unfussy. Flake and small granules make a good staple, with regular feeds of small live and frozen foods such as Daphnia and bloodworm.

Breeding

Easy to breed. Males are slimmer and smaller than females, with more pointed dorsal and anal fins. Condition pairs separately on good live and frozen food at about 24–25.5 °C, then move them to a dimly lit spawning tank of about 45 × 30 × 30 cm, kept a few degrees warmer (around 28–30 °C) with slightly acidic water. Provide java moss or spawning mops, or mesh over the base so the eggs fall out of reach. Remove the adults as soon as eggs are seen as they will eat them. Eggs hatch in 18–36 hours and the fry swim freely a few days later. Keep the tank dim, as eggs and young fry are light-sensitive, and start them on infusoria, then microworm or brine shrimp nauplii.

Compatibility and tank mates

Generally fine in a community of robust fish such as livebearers, danios, rasboras, other tetras, Corydoras and sturdier dwarf cichlids. They have a reputation as fin nippers, so avoid slow, long-finned fish like bettas, fancy guppies and angelfish, especially if the group is small.

Last updated 4 October 2026. Community-edited care guide on Aquatic-Auctions.

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