Black Tetra

Black Widow Tetra, Blackskirt Tetra

Family: Characidae Blackskirt Tetra, Gymnocorymbus ternetzi, Black Widow or Black TetraGymnocorymbus ternetziPhoto © Animal-World: Courtesy David Brough
Latest Reader Comment - See More
i have had black skirt tetra's for years,recently one become ready to lay egss,i put her in a breeding tank,within 3-4 days she seemed to lay eggs,becoming thin... (more)  T.J.

First introduced into the United States in the 1930's, the Blackskirt Tetra is one of the most popular aquarium fish!

The Black Tetra Gymnocorymbus ternetzi is also known as the Black Widow Tetra or Blackskirt Tetra. It's a good fish for the beginner because it is very hardy, undemanding, and easily bred. This tetra is a real beauty in a community aquarium. It is very active and fast moving. It can tend towards fin nipping its tank mates however, so because of this it should not be kept with smaller fishes. But it will do very well in a community tank with larger fishes.

Being a schooling fish the Black Tetra will appreciate the company of its own kind. The standard school size for the aquarium is 7, and they will do well with that many or even more or their own. They also like a well lit tank with dense areas of bunched low vegetation which will leave lots of open areas to swim in. They are hardy at 70° F to 90° F, but are prone to develop ick if kept in colder temperatures.

This is not the only tetra known as a Black Tetra. This fish is not to be confused with its cousin Gymnocorymbus thayeri, also called the Black Tetra. The G. thayeri is a shyer fish and not as hardy as the Blackskirt. it is similar in appearance to the Black Widow, but is lighter with not as bold a coloration and it lacks the vertical striping. It also has a more convex anal fin rather than rounding out.

There are some very nice varieties of the Black Skirt Tetra that have been developed as well. A popular variation is the Longfin Blackskirt Tetra. Then there are some color morphs that offer a unique look. These include the White Tetra or Goldenskirt Tetra which has become very common and also the Colored Skirt Tetra.

For Information on keeping freshwater fish, see:
Freshwater Aquarium Guide: Aquarium Setup and Care

Geographic Distribution
Gymnocorymbus ternetzi
Data provided by
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Characiformes
  • Family: Characidae
  • Genus: Gymnocorymbus
  • Species: ternetzi
Black Skirt Tetra

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Both long and short finned varieties of the Black Skirt Tetra.

Black Tetra - Quick Aquarium Care
  • Size of fish - inches: 2.2 inches (5.51 cm)
  • Minimum Tank Size: 15 gal (57 L)
  • Temperament: Semi-aggressive
  • Aquarium Hardiness: Very Hardy
  • Temperature: 70.0 to 79.0° F (21.1 to 26.1° C)
  • Aquarist Experience Level: Beginner
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Habitat: Distribution / Background

The Black Tetra Gymnocorymbus ternetzi was described by Boulenger in 1895. The species is not listed on the IUCN Red List. Other common names it is known by are the Black Widow Tetra and the Blackskirt Tetra.

They are found in South America in Paraguay and Guapore Basins where they inhabit the upper layers of the water feeding on worms, small crustaceans and insects  These tetras show a preference to small, slow moving creeks, streams and tributaries that are well shaded from the forests canopy. Many are captive bred for the aquarium industry.

  • Scientific Name: Gymnocorymbus ternetzi
  • Social Grouping: Groups
  • IUCN Red List: NE - Not Evaluated or not listed


The Blackskirt Tetra is a deep-bodied species and laterally compressed. This fish will reach about 2 1/4 inches (5.5 cm) in the home aquarium, but will breed at just 1 1/2 inches. It has a lifespan of about 6 - 7 years. It is distinguished by two vertical stripes and by what appears to be overly developed dorsal and anal fins. These make it appear as if though it has a "skirt", with most of its mass on the bottom half of the body. The fine black color changes to a gray in the adult.

Various strains of the Blackskirt Tetra have also been developed:

  • Long-finned Varieties
    A long-finned variety, the Blackskirt Hifin Tetra, was first developed in Europe. It is also very popular and is readily available. These fish are a bit more difficult to breed than the Blackskirt Tetra, probably because of their being highly inbred already. They are also referred to as the Longfin Blackskirt Tetra, Long-fin Black Widow or Longfinned Black Tetra.

  • Colored Varieties
    Strains in a natural white, pink, and blue have also been developed. Of these the White Tetra or Goldenskirt Tetra has become very common followed by the Colored Skirt Tetra. It is sometimes artificially dyed in various pastels colors and sold as a Colored Tetra or under various colored names such as the Blueberry Tetra, Strawberry Tetra, or Rainbow Tetra.
  • Size of fish - inches: 2.2 inches (5.51 cm) - These fish get up to 2 1/4 inches (5.5 cm) but will breed at 1.5 inches.
  • Lifespan: 7 years - They have a life span of about 6-7 years.

Fish Keeping Difficulty

The Black Tetra is a hardy fish that is great for the beginner fish keeper. They adapt very well to water condition changes. They make great tank mates for most community tanks.

  • Aquarium Hardiness: Very Hardy
  • Aquarist Experience Level: Beginner

Foods and Feeding

Since they are omnivorous the Blackskirt Tetra will generally eat all kinds of live, fresh, and flake foods. To keep a good balance give them a high quality flake food everyday. Feed brine shrimp (either live or frozen) or blood worms as a treat.

  • Diet Type: Omnivore
  • Flake Food: Yes
  • Tablet Pellet: Yes
  • Live foods (fishes, shrimps, worms): Some of Diet
  • Vegetable Food: Some of Diet
  • Meaty Food: Some of Diet
  • Feeding Frequency: Several feedings per day - Offer only what they can consume in 3 minutes or less with multiple feedings per day.

Aquarium Care

The Black Tetra is easy to care for provided the water is kept clean. Aquariums are closed systems and regardless on size all need some maintenance. Over time decomposing organic matter, nitrates and phosphate build up and the water hardness increases due to evaporation. To combat these ever changing conditions water should be replaced on a regular basis. At least 25 - 50% of the tank water should be replaced every other week, especially if the tank is densely stocked.

  • Water Changes: Bi-weekly

Aquarium Setup

Because they are very active swimmers it is also advisable to keep Black Tetras in a tank at least 20 inches long and ideally 15 or more gallons. They like a soft, peat-filtered water. These fish prefer some plant cover and a darker gravel substrate, but  they also need open areas to swim freely. Additionally, the tank should be securely covered as these fish are skilled jumpers and will probably do so if given the opportunity. 

To get the best out of this fish, set up a biotype tank. For the substrate use a river sand with some drift wood and twisted roots. Add some dried leaves to the sand, which will stain the water a light brown and replace leaves every few weeks. Use dim lighting and it will develop the tetras best coloring.

  • Minimum Tank Size: 15 gal (57 L) - Fifteen gallons is the least amount of space advisable to host a small school.
  • Suitable for Nano Tank: Yes
  • Substrate Type: Any
  • Lighting Needs: Moderate - normal lighting
  • Temperature: 70.0 to 79.0° F (21.1 to 26.1° C)
  • Range ph: 5.8-8.5
  • Hardness Range: 3 - 30 dGH
  • Brackish: No
  • Water Movement: Moderate
  • Water Region: All - These fish will swim in all areas of the aquarium.

Social Behaviors

They are active and can be semi-aggressive fin nippers.  Fin nipping can be kept down by keeping them in schools of atleast 8 or more.  In large groups they will focus on each other. They should be kept in a community aquarium with fish the same size or larger. With age they become a more sedentary fish.  These tetras do well with most livebearers, danios, rasboras, other tetras, peaceful bottom dwellers and some dwarf cichlids.

  • Venomous: No
  • Temperament: Semi-aggressive - Relative to other tetras, Black Tetras have a tendency to be slightly more aggressive and being a fin nipper is not uncommon among this species.
  • Compatible with:
    • Same species - conspecifics: Yes
    • Peaceful fish (): Monitor - Watch for stress in other fish caused by Black Tetra fin nipping.
    • Semi-Aggressive (): Threat
    • Aggressive (): Threat
    • Large Semi-Aggressive (): Threat
    • Large Aggressive, Predatory (): Threat
    • Slow Swimmers & Eaters (): Monitor
    • Shrimps, Crabs, Snails: Safe - not aggressive
    • Plants: Safe

Sex: Sexual differences

Picture of a Black Tetra,  Black Widow, or Blackskirt Tetra
Photo Courtesy: Fish2U

The male's dorsal fin is more narrowed and more pointed. Also, the male's frontal portion of the "skirt" or anal fin is noticeably broad while the female's "skirt" tends to run parallel to the stomach line. A mature female is also more plump.

Breeding / Reproduction

The Black Tetra, Black Widow, or Blackskirt Tetra are egg layers. They are easily breed with a good pairing. The biggest challenge is that the young are prone to starving to death if they are in a dark tank and can't find a food source. The fry should have plenty of light, both day and night, until they are large enough to eat freshly hatched brine shrimp. . For a description of breeding characin fish, see Breeding Freshwater Fish: Characins.

  • Ease of Breeding: Easy

Fish Diseases

As with most fish the Black Tetra are prone to skin flukes, parasitic infestations (protozoa, worms, etc.), ichthyobodo infection, parasitic infestations (protozoa, worms, etc.), bacterial infections (general), and bacterial disease. Black Tetra are extremely hardy and disease is not usually a problem in a well maintained aquarium. That being said there is no guarantee that you won't have to deal with health problems or disease. Remember anything you add to your tank can bring disease to your tank. Not only other fish but plants, substrate, and decorations can harbor bacteria. Take great care and make sure to properly clean or quarantine anything that you add to an established tank so not to upset the balance.

A good thing about Black Tetra is that due to their resilience, an outbreak of disease can often be limited to just one or a few fishes if you deal with it at an early stage. When keeping more sensitive types of fish, it is common for all fishes to be infected even before the first warning signs can be noticed. The best way to proactively prevent disease is to give your Black Tetra the proper environment and give them a well balanced diet. The closer to their natural habitat the less stress the fish will have, making them healthier and happy. Stressed fish are more likely to acquire disease.

For information about freshwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments. This is a great source for information on disease and treatments. It is recommended to read up on the common tank diseases. Knowing the signs and catching and treating them early makes a huge difference. Black Tetra are very resilient.


The Black Tetra, also sold as the Blackskirt Tetra or Black Widow, is readily available and inexpensive.


Author: David Brough CFS, Clarice Brough CFS, Jeremy Roche
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Lastest Animal Stories on Black Tetra

T.J. - 2013-01-06
i have had black skirt tetra's for years,recently one become ready to lay egss,i put her in a breeding tank,within 3-4 days she seemed to lay eggs,becoming thin again..i removed her,returning her to the community tank,how long do eggs take to produce fry,what do eggs look like?

  • Jeremy Roche - 2013-01-07
    They are nearly transparent when they have just been released, and will hatch after 22-30 hours. It will take the fry 3-4 days to become free swimming.
Thomas Pietruszka - 2010-01-18
Black Tetras are superb fish for newbies, but they are also excellent fish for the best of display tanks. I have a large school of them in a 300 gallon show tank in our living room; they are heavenly and get along great with the other community fish within the tank (i.e., Glowlight Tetras, Bloodfins, Buenos Aires Tetras, Red Glass Barbs, and Flame Tetras). I've had gorgeous Discus fish and Angel fish for years, in the show tank... but the masses of Black Tetras and other fish are just as beautiful, in their own way! I've had tropical fish since my grade school years; I'm now around 60 years old... and I know top quality fish when I see them. These pert, black beauties may be common and inexpensive... but as Walt Whitman sagaciously suggested... some of the best things in life are free. These fish, like flat miniature versions of Silver Dollars, carry themselves well, looking like content butterflies. They are never aggressive when kept in larger groups. They are very hardy and stay out at the front of the tank, displaying well. I even have a picture of one for the wallpaper for my computer!

Katie - 2009-11-27
I have two black-skirt tetras in a ten gallon tank. These fish were kept with three danios (two long finned), two ghost shrimp, an ADF, and one chinese alge eater. These tetras DO NOT like long-finned fish. It nipped at my betta's tail when he was in the tank, and had recently killed one of my danios, I give the other one till the morning... his fin has been nipped at and is frayed from the ends. The small finned danio is fine. Also the chinese alge eater loves them. They are great fish to keep, i just suggest that you try not to add new fish, nor put them with long-tailed fish.

  • Skeith - 2010-06-24
    Well if your danios are slow, they will be attacked. I've researched a lot of fish and the Black Tetra will nip at slow moving fish and acts aggressively towards them. Be careful.
  • Anonymous - 2011-12-29
    Add a compatible tropical fish. Add in even numbers. Not in odd!!
Kamperoni - 2009-01-23
I have 6 of these guys in a 29 gallon with a pair of Kribs. and some Serpae tetras and they're great! I found that the bigger the group they're in, the more they just bother their own kind instead of everyone else. Although they do nip each other a lot, torn fins can be expected though it never gets worse than that, and the damage is never very bad, heals in a few days actually. If they're happy they turn really dark and look very good. All in all, they're an entertaining and fun fish to have.

Deedee - 2005-03-03
Have 11 of these active and nice fish in my heavily planted 30 gallon. They are rambunctious dancers when they see their dinner coming and always hungry for more any time of night or day it seems. Their tank offers plenty of plants on a CO2 controller and a nice mopane bog wood root. Tankmates include two pearl gouramis and a handful of cories which they all mostly ignore in favor of thinking about food and feeding times and whether anyone walking by might have a morsel for them. Very nice to see that tank so lively again, those two particular pearls hide their lives away, so the blackskirts give the tank life now. Great fish, pleasure to have.

Bob Doetsch - 2005-04-06
The info here is very helpful to us newbie aquarium hobbyists. We just started our 20 gallon high tank with three Black Tetras. At first they were reserved and confined themselves to an area of cover. We are one day into this now, and they are more comfortable, alternate between hanging around the plastic leaves and darting around, occasionally nipping at each other. We are told to wait at least a week before adding more fish. We had a false start dealing with a chain pet store before we wised up and visited a real fish store with expert advice.

-Bob in St. Clair Shores, Mich.


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