Black Skirt Tetra

Gymnocorymbus ternetzi

Also known as: Black widow tetra, Black tetra, Petticoat tetra

Water Parameters

• Temperature: 20–26°C
• pH: 6–7.5
• Hardness (GH): 36–268 ppm (2–15 dGH)

Values above are general hardness (GH). For carbonate hardness (KH), the buffer that keeps pH stable, see the water parameters guide.

Care Summary

An old aquarium standby: tough, inexpensive, and forgiving of the parameter swings that kill more delicate species, which is why it survives in tanks that neglect other fish. The tall, finned, charcoal-and-silver body is distinctive, greying as the fish matures. Avoid the dyed fruit-tetra and genetically modified GloFish versions where you can: the former are injected with colour and tend to be short-lived, the latter are the same fish with the same care needs. Kept in a proper school with appropriate tankmates, black skirts are reliable, active, and undemanding, and a sensible choice for a first community tank that is not stocked with flowing fins.

Tankmates

Hardy and adaptable, but with an asterisk: black skirts can nip trailing fins, particularly when kept in groups too small to occupy them with their own social order. A group of six or more, with space to school, keeps the behaviour in check; pairs and trios are the troublemakers. For that reason they are a poor match for slow, long-finned tankmates such as bettas, fancy guppies, angelfish, and the larger gouramis. They pair well with other robust, similarly-sized, fast-moving fish. Their colour fades with age, from the deep black of juveniles to a translucent grey, which is normal and not a sign of illness.

Compatible with

• Zebra Danio
• Bronze Corydoras
• Bristlenose Pleco
• Harlequin Rasbora
• Platy
• Swordtail
• Cherry Barb
• Red Eye Tetra
• Penguin Tetra
• Silvertip Tetra

Avoid keeping with

• Betta
• Dwarf Gourami
• Pearl Gourami
• Honey Gourami
• Guppy
• Angelfish
• Long Finned Species

Common Problems

• fin nipping in groups smaller than 6
• natural colour fading with age (not illness)
• ich
• stress in undersized groups

Sources: seriouslyfish.com, fishbase.org · Last updated: 2026-06-20