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.
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:
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.
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.
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
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
Water Movement: Moderate
Water Region: All - These fish will swim in all areas of the aquarium.
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.
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.
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
Sex: Sexual differences
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
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.
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.
Jason Wicklund - 2012-01-08 Hey I have a 20 gallon with 5 black skirt tetras, 1 shubunkin goldfish, two bumble bee platies, 1 Bala Shark, 2 plecos, 1 guppy, 1 Cichlid, and 3 tiger barbs. My fish are very good together. The only problem I have is that My tetras aren't eating and I've only had them a day... Is that normal for them not to eat the first couple days?
Anonymous - 2012-12-25 The tiger barbs are probably stressing them
Anonymous - 2012-12-25 Yeah they need to be kept in groups of at least six. If the cichlid is from Africa it could also stressing them out
Rebecca - 2012-12-04 Quick question. Ok, I have eight black skirt tetras in a 20 gallon long aquarium, along with four 3-lined corydoras and a mystery snail. One of my black skirts is a lot bigger than the others, but I bought them all together about a week ago (the tetras). Anyhow, this morning there are 5 of the smaller ones that are constantly swarming the bigger one. Is this normal for them? Should I be worried for the big one?
Jeremy Roche - 2012-12-04 They are school fish so it is pretty normal.
brady - 2012-08-07 Well I have a black tetra and I got him at walmart. He was the biggest and the fastest. He is as cute as ever. Right now he seems to not be eating can someone please help me. Well my mom forgot the filter. I've been thinking that was the problem. I just love him too much to let him die because I got him last year not too long ago so anyways if you help me I will be gratefull for that. So if you did. Thank you I appreceate that so bye see you later maybe I don't know well bye.
Jeremy Roche - 2012-08-08 Is this a new tank set up? I would get a water tester and a filter. Water conditions as a tank cycles will greatly affect a fish.