Black skirt tetra

Quick facts

Adult size

6 cm

Lifespan

can live up to 6 years; hardy; 5-6 years routine

Tank zone

mid

Temperament

semi-aggressive

Difficulty

beginner

Schooling

recommended 6+ (critical minimum 5, thrives at 10+)

Water parameters

Temperature

22–28°C

pH

5.5 to 7.5

Hardness

2 to 18 dGH

Tank requirements

Minimum volume

110 L

Minimum length

75 cm

Flow

low

Lighting

dim preferred

Substrate

any

Hiding spots

needed

Open swimming room

needed

Feeding

Diet: omnivore, feeds primarily at the mid.

Eats anything offered: flake, pellets, frozen bloodworm, frozen brine shrimp, frozen daphnia, live food, blanched vegetables. Not picky, not slow, not shy about competing for food. In community tanks they eat their share and then some. Standard twice-daily feeding in moderate amounts. Color and fin condition improve with a varied diet that includes frozen and live food alongside dry staples.

Compatibility

• Hardy, active, and slightly pushy. Not a fin-nipper in the classic tiger-barb sense, but juveniles occasionally chase and nip slow-moving tankmates. This behavior fades in adults, especially in larger groups.
• Best in groups of 6+ with robust, mid-sized tankmates: other tetras, barbs, rainbowfish, and catfish. Avoid pairing with long-finned species (bettas, angelfish, fancy guppies); the flowing fins trigger occasional chasing.
• Sold under a confusing array of trade names: black skirt tetra, black widow tetra, petticoat tetra, and as color-dyed or GloFish variants. The GloFish versions (fluorescent pink, green, orange) are genetically modified Gymnocorymbus ternetzi and have the same care requirements.
• One of the most commonly recommended tetras for beginners because it tolerates a wide range of water conditions, eats anything, and is virtually indestructible.

Habitat

Native to the Paraguay and Guapore River basins in Brazil, Argentina, and Bolivia. Found in slow-moving tributaries with overhanging vegetation and sandy to muddy substrates. The species was described in 1895 and has been a staple of the aquarium trade since the 1930s. Juveniles are jet-black with pronounced vertical bars and a large, flowing anal fin that gives them the "skirt" appearance. As the fish matures (3+ years), the black fades to gray, which disappoints keepers who bought them for the dramatic juvenile coloring. Males are smaller and slimmer with a broader anal fin; females are rounder-bodied. The species is bred commercially on a vast scale, including as the base species for GloFish fluorescent variants and various dyed color forms ("blueberry tetra," "strawberry tetra"). Dyed fish lose their artificial color over time and the dyeing process causes stress and potential organ damage. Avoid buying obviously dyed fish. The natural form is the most attractive anyway.

Breeding

Egg scatterer, and one of the easier tetras to breed in captivity. Condition a pair with frozen food for a week. The breeding tank should have fine-leaved plants or spawning mops, soft water (GH below 8), and a temperature of 26–27°C. Spawning happens at dawn, often triggered by light hitting the tank. The pair scatters 300-500 eggs among the plants. Eggs are semi-adhesive. Adults eat eggs, so remove them after spawning. Eggs hatch in 24-36 hours. Fry are relatively large for a tetra and can eat baby brine shrimp within a few days of becoming free-swimming. Growth is fast; juvenile coloring appears within 3-4 weeks. Black skirt tetras are bred on a massive commercial scale using outdoor ponds and hormone-induced spawning. Home breeding is a reasonable project for intermediate keepers.

Common problems

Color fading with age is the most common complaint. Juvenile black skirts are strikingly dark; adults over 2-3 years fade to a gray that looks nothing like what was in the store. This is natural and not a sign of illness. Maintaining dark substrate and subdued lighting slows the fading slightly but doesn't prevent it. Ich is common in newly purchased fish, especially from chain stores where turnover is high and stress levels are elevated. Standard ich treatment works; the species tolerates medication well. The GloFish variants occasionally develop tumors, which may be related to the genetic modification process, but data is limited. Nipping behavior in small groups is the behavioral concern; it resolves in groups of 8+.

Bioload

Bioload coefficient: 1.8 (deep-bodied tetra; per-cm load slightly higher than slim tetras).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size