Tetras · Gymnocorymbus ternetzi

Black skirt tetra care guide

Also called: Black widow tetra, Black tetra, Petticoat tetra, GloFish tetra, White skirt tetra, Long-fin black skirt tetra

The black skirt tetra is a hardy, deep-bodied tetra with a large black anal fin, and it is the fish behind the colorful GloFish tetra. It suits beginners, but keep a group of 8 or more so it doesn't nip long-finned tank mates.

Black skirt tetras need a tank of at least 20 gallons (76 L), a group of 8 or more, and water at 22–26°C (72–79°F) with a pH of 6–7.5. They grow to about 6 cm (2.4 in) and are peaceful.

Plan a tank with black skirt tetrasSee all tank mates

Black skirt tetra quick facts

Scientific nameGymnocorymbus ternetzi
FamilyAcestrorhamphidae
OriginParaguay and Guaporé river basins, South America (most are farm-bred; GloFish tetras are captive-bred only)
Adult size6 cm (2.4 in)
Minimum tank20 gallons (76 L), at least 75 cm (30 in) long
Temperature22–26°C (72–79°F)
pH6–7.5
Hardness (GH)5–18 dGH
Group size8 or more (shoaling fish)
TemperamentPeaceful
Swims atMiddle
DietOmnivore
Care levelEasy
Lifespan3–5 years
Safe with shrimp?No, eats shrimp
Safe with plants?Yes

Tank setup

A group of 8 needs at least a 20-gallon (76 L) tank about 30 in (75 cm) long, and bigger groups need more room. Leave open swimming space in the middle and put plants or decor along the back and sides. A dark substrate makes their black fins stand out.

How many black skirt tetras in a tank?

The smallest common tank that suits black skirt tetras is a 20 gallon long. Here is roughly how many fit in each size when they are the only fish, based on adult size and waste output. Leave room if you want tank mates.

TankBlack skirt tetras (alone)
3 gallonToo small
5 gallonToo small
10 gallonToo small
15 gallonToo small
20 gallonToo small
20 gallon long8–13
29 gallon8–19
40 gallon8–26
55 gallon8–37
75 gallon8–50
125 gallon8–84

What you need for black skirt tetras

Sized for a 20 gallon long tank, the smallest common size that suits a group of 8 black skirt tetras. For a different tank or a mix of fish, use the stocking calculator for a list sized to your plan.

Tank and equipment

Food and extras for black skirt tetras

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Water parameters

Keep the water at 72–79°F (22–26°C) with a pH of 6.0–7.5. Almost all are farm-bred, so they handle soft to fairly hard tap water well. Use a heater, a good filter and weekly partial water changes.

Best tank mates for black skirt tetras

These popular species share black skirt tetras' water needs and temperament. See the full list of 86 good matches.

Avoid keeping black skirt tetras with

  • Cherry shrimp: Black skirt tetra eats small shrimp like cherry shrimp.
  • Oscar: Oscar can eat black skirt tetras: they're small enough to fit in its mouth once it's grown.
  • Chinese algae eater: Chinese algae eater is aggressive and will bully or injure peaceful black skirt tetras.
  • Convict cichlid: Convict cichlid is aggressive and will bully or injure peaceful black skirt tetras.
  • Discus: They need different temperatures: Black skirt tetra 22–26°C (72–79°F), discus 28–30°C (82–86°F).
  • Electric yellow cichlid: Electric yellow cichlid is a Lake Malawi cichlid. It needs a Lake Malawi tank: hard, alkaline water (pH 7.5–8.5), plenty of rockwork and other cichlids from the same lake. Black skirt tetras don't belong in that setup.

Feeding

They are easy-to-feed omnivores. Use a quality flake or micro pellet as the staple, and add frozen or live bloodworms, daphnia and brine shrimp a few times a week. Feed small amounts once or twice a day.

Behavior

Black skirts are lively and mostly peaceful, but they have a reputation for nipping fins, mainly in small groups. Keep at least 8, and 10–12 is better. Avoid slow, long-finned fish such as bettas, angelfish and fancy guppies. Danios, other mid-sized tetras, platies, corydoras and small plecos are good matches.

Breeding

They scatter eggs over fine-leaved plants and give no parental care. Use a separate, dim tank with java moss, a spawning mop or mesh on the bottom, and slightly warmer, softer water. Remove the adults once eggs appear, because they eat them. Feed the fry infusoria first, then baby brine shrimp.

Tips from experienced keepers

  • Keep 10 or more if you have room. Bigger groups keep their chasing within the school instead of picking at tank mates.
  • Skip bettas, angelfish and fancy guppies. Their long, slow fins are an easy target.
  • GloFish tetras need the same care as normal black skirts. Blue light makes them glow, but turn it off at night so they can rest.
  • Avoid dyed or painted tetras. Artificial dyeing stresses the fish and often shortens their lives.
  • Cherry shrimp and other dwarf shrimp may be eaten. Larger amano shrimp usually fare better.

Frequently asked questions

How many black skirt tetras should be kept together?

Keep at least 8, and 10–12 is better. In small groups they get stressed and are more likely to nip other fish.

Are GloFish tetras the same as black skirt tetras?

Yes. GloFish tetras are black skirt tetras with an added fluorescent protein gene, which they pass on to their young. They need the same tank, water and food as regular black skirts.

Can black skirt tetras live with bettas?

It's not a good idea. Black skirts often nip long, flowing fins, and a slow betta is an easy target. Choose fast, short-finned tank mates instead.

Sources

We checked these references when writing this page. Values are for healthy long-term keeping, not survival limits. Last reviewed 2026-10-13. See our editorial policy.