Black skirt tetra

A silver tetra with a black skirt and a calm temper. While the shoal is large it leaves its neighbours alone; in a small group it starts nipping fins.

Gymnocorymbus ternetzi · Characins · updated 11 November 2026

What it is and where it comes from

The black skirt tetra comes from South America: the Paraguay, Guaporé and Rio Negro basins, in slow streams under the tree canopy. Boulenger, a Belgian, described it in 1895; it reached Europe in 1933 and soon became common.

No wild black skirt tetras are sold; all are farm-bred. Juveniles are almost black, and the "skirt" fades to grey with age. Males are smaller and blacker, with a pointed dorsal fin, while the female's is taller and rounder. Besides the plain form there are veiltail, albino, the genetically modified GloFish and artificially dyed "caramel" fish, which get the paint by syringe. Their colour fades with time, and they usually live less.

Housing and conditions

A tank from 60 l (16 gal), with a 75×30 cm footprint preferable. Temperature 22–26 °C (72–79 °F): Russian Wikipedia says 25–27 °C, Seriously Fish 20–26 °C, and practice sits closer to 23–25 °C. pH 6.0–7.5, hardness 5–15 °dGH, though the fish tolerates harder water. Weak current, a quiet filter.

Dim light, and floating plants above are very welcome. Thickets along the sides and back wall, the middle left open: black skirt tetras like to cruise along the glass. Dark substrate, from sand to fine gravel. A lid is needed, as the fish jumps.

Feeding

Omnivorous; in the wild it takes insects at the surface. In an aquarium, flakes, granules, daphnia, bloodworm, brine shrimp. In summer live cyclops is worth giving: it cleans the gut and keeps the colour. A portion in 2 minutes, once or twice a day.

Overfeeding shows as a round belly: the fish swims heavily and hangs near the bottom. Black skirt tetras tend towards obesity, and fat presses on the swim bladder. Uneaten food also rots and raises nitrate.

Lifespan

5–7 years in good conditions. English Wikipedia gives 3–5 years, Tetra 6–7, and the gap is explainable: temperature and the form of the fish decide much of it. Veiltail and dyed specimens often live shorter lives than plain silver ones.

Temperament and tank mates

Peaceful and shoaling, with a caveat: in a small group it starts nipping its neighbours' fins. Keep 8–10, and the quarrels stay inside the shoal.

Tank mates: zebrafish, tetras, mollies, swordtails, corydoras, bristlenose plecos. Not: veiltail bettas and guppies, small shrimp and fry, large cichlids. Veiltail fins get nipped, and small livestock is eaten.

Diseases

Most common:

• Ich: white dots over the body, the fish rubs against decor. Treated with antiparasitic medication as directed; temperature stays below 26 °C.
• Fin rot: fin edges turn white and tear. In veiltail forms it starts after nipping and dirty water.
• Obesity: a round belly, shortness of breath, refusal to move. Fasting days and smaller portions help.
• Fungus at an injury: a cottony growth within a couple of days. Clean water changes and an antifungal are needed.

A vet makes the diagnosis; antibiotics at random do harm.

Breeding

An egg scatterer with no care for the brood. Spawning tank 30–40 l, moss or a grid on the bottom, water 24–26 °C, hardness about 4 °dGH, pH 7.0. The male goes in first, the female a few hours later, and spawning happens in the morning. She lays 500–1000 eggs, and the breeders come out at once. Larvae hatch in 24–36 hours and the fry swim on day 3–5. They grow fast, but have to be sorted by size, or the big ones outcompete the small ones.

Who it suits

A beginner with a tank from 60 l: the fish is tough, eats anything and needs no exotic parameters. Minus: it grows to 5 cm, nips fins in a cramped shoal, and jumps. It does not suit a nano tank or a company of veiltail fish. To see how many your tank can hold, use the calculator.