Black Widow Tetra – Size | Male | Female | Tank | Eggs | Traits

Black Widow Tetra
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The Black Tetra Gymnocorymbus ternetzi is also referred to as the Black Widow Tetra or Blackskirt Tetra. It’s a great fish for the newbie as a result of it is rather hardy, undemanding, and simply bred.

Black Widow Tetra profile

This tetra is an actual magnificence in a community aquarium. It may be very lively and fast-paced. It generally is a fin nipper, nevertheless, so it shouldn’t be saved with smaller fishes however will do very effectively in a community tank with bigger fishes.

A schooling fish, the Black Tetra will admire the company of its personal form. The standard school size for the aquarium is 7 people, and they’re going to do effectively with that many and even more of their very own.

They like a well-lit tank with dense areas of bunched low vegetation, leaving a number of open areas to swim in. They are hardy at 70° F to 90° F, however are vulnerable to develop ich if saved in colder temperatures.

Origin and Distribution

Black widow tetras originate from the small, slower tributaries and creeks of the Guapore and Paraguay Rivers in Brazil, the place the forest cover gives each shade and meal.

They congregate close to the floor of the water the place they eat bugs, crustaceans, and small worms. Originally they have been solely obtainable as wild-caught, however, all specimens offered now are totally captive-bred, resulting in a lot of new man-made variations of this popular fish.

Other variants of the black widow tetra embody the longfin blackskirt tetra, the goldenskirt tetra, and the colored skirt tetra.

Additionally, related species have typically been mistaken for this fish, together with Socolof’s tetra (Gymnocorymbus socolofi) and the false black tetra (Gymnocorymbus thayeri).

Both of those species should not as often obtainable within the aquarium commerce, nor are they as popular because of the black widow tetra.

Black Widow Tetra Description

The Blackskirt Tetra is a deep-bodied species and laterally compressed. This fish will attain about 2 1/four inches (5.5 cm) within the dwelling aquarium however will breed at simply 1 half inches.

It has a lifespan of about 6 to 7 years. It is distinguished by two vertical stripes and by what seems to be overly developed dorsal and anal fins.

These make it seem as if although it has a “skirt,” with most of its mass on the underside half of the body. The effective black colour of the juvenile fades to a grey because it matures.


Potential confusion comes from the truth that this isn’t the one fish often known as a Black Tetra. This fish is to not be confused with its cousin Gymnocorymbus thayeri, which can be known as the Black Tetra.

The G. thayeri is a shyer fish and never as hardy because of the Blackskirt. It is comparable in look to the Black Widow however lighter with more delicate coloration and missing the vertical striping. Its anal fin can be more convex than the Blackskirt’s.

Black Widow Tetra Diet and Feeding

Black widow tetras readily settle for nearly any meals, together with stay, recent, frozen, freeze-dried, or flake meals.

For the breed’s optimum health, present a wide range of meals, which might embody high-quality flake meals, brine shrimp, and any kind of worms, in addition to vegetable dietary supplements and spirulina.

Colors and Markings

One of the best-known members of the tetra family, the black widow tetra is definitely acknowledged by the distinctive black dorsal and anal fins, and by the vertical black stripes on the body.

Naturally occurring color variations will be white to pinkish-hued. But a lot of totally different colored strains, in addition to long-finned varieties, have been produced by captive breeding.

Don’t be fooled by any variety of pastel-colored specimens; these fish have been achieved with dyes. Avoid any people that will have been artificially colored as they’re much more vulnerable to illness.

Contrary to some studies, the process of dying is aggravating to the fish, and this stress shortens its lifespan a great deal. Purchasing these fish solely serves to help this unethical and dangerous observe.

Black widow tetras stay comparatively small, reaching an adult size of roughly two inches. Hybrids, such because the long-finned varieties, are typically a bit bigger.

Once the black widow tetra achieves its mature size at roughly one year, its regular darkish coloration will slowly start to fade right into a silvery grey.

By the time the fish has reached 5 years or more in age, it’s normally fairly pale in color. These fish additionally pale when they’re pressured or unwell.

Fish Keeping Difficulty

The Black Tetra is a hardy fish that’s great for the start fish keeper. They adapt very effectively to water situation adjustments and make a great addition to most community tanks.

Aquarium Hardiness: Very Hardy
Aquarist Experience Level: Beginner


An education fish by nature, black widow tetras are finest saved in teams of six or more. They make a superb community fish on account of their peaceable nature.

Some house owners report that they often nip the fins of slower-moving fish, notably these with long, flowing fins corresponding to bettas or angelfish.

Black Widow Tetra Habitat and Care

Black widows are an undemanding species that adapt to a range of circumstances, although subdued lighting and neutral-colored gravel substrates are most popular.

They are accustomed to massive crops of their natural habitat and revel in a well-planted aquarium with some open swimming area.

Although not demanding about water, they like gentle, acidic water, ideally tannin-stained. Ideally, it’s best to initially match them to the water circumstances from the provider, as sudden adjustments should not be tolerated by this species. Colder water can stress tetras, leaving them fairly weak to a lot of ailments corresponding to Ich.

Aquarium Care

The Black Tetra is straightforward to look after offering the water is saved clear. Aquariums are closed methods, and no matter size, all need some upkeep.

Over time, decomposing natural matter, nitrates, and phosphate construct up and the water hardness will increase on account of evaporation.

To fight these ever-changing circumstances, water must be changed on a regular basis. At least 25 to 50% of the tank water must be changed each different week, particularly if the tank is densely stocked.

Water Changes: Bi-weekly

Black Widow Tetra Aquarium Setup

Because they’re very lively swimmers, Black Tetras must be saved in a tank at the least 20 inches long and ideally 15 or more gallons. They like soft, peat-filtered water.

These fish choose some plant cover and a darker gravel substrate, however in addition they need open areas to swim freely. Additionally, the tank must be securely coated as these fish are expert jumpers and can most likely achieve this if given the chance.

To get the very best out of this fish, arrange a biotype tank. For the substrate, use river sand with some drift wooden and twisted roots.

Add some dried leaves to the sand, which is able to stain the water a light brown, and substitute the leaves every few weeks. Dim lighting will develop the Black Tetra’s coloring to the finest impact.

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Minimum Tank Size: 15 gal (57 L) – Fifteen gallons is the smallest size advisable to maintain a small school.
Suitable for Nano Tank: Yes
Substrate Type: Any
Lighting Needs: Moderate – regular lighting
Temperature: 70.Zero to 79.0° F (21.1 to 26.1° C)
Breeding Temperature: 82.0° F – These fish will spawn at 82 to 86° F (27.Eight to 30° 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.

Black Widow Tetra Social Behaviors

The Black Tetra is an active fish and generally is a semi-aggressive fin nipper. Fin nipping will be discouraged by holding them in faculties of at the least 8 or more people.

In massive teams, they may deal with one another moderately than on smaller fish. They must be saved in a community aquarium with fish the identical size or bigger.

With age, they turn out to be more sedentary. These tetras do effectively with most livebearers, danios, rasboras, different tetras, peaceable backside dwellers, and a few dwarf cichlids.

Venomous: No
Temperament: Semi-aggressive – Relative to different tetras, Black Tetras tend to be barely more aggressive. Fin nipping will not be unusual amongst this species.
Compatible with:
Same species – conspecifics: Yes
Peaceful fish (): Monitor – Watch for stress in different fish brought on by Black Tetra fin nipping.
Semi-Aggressive (): Threat
Aggressive (): Threat
Large Semi-Aggressive (): Threat
Large Aggressive, Predatory (): Threat
Slow Swimmers & Eaters (): Threat – Tetras will out-compete them for meals.
Shrimps, Crabs, Snails: Safe – not aggressive
Plants: Safe

Gender Differences

Female black widows are usually bigger than males and have a rounder body. In the feminine, the anal fin runs parallel with the vertical black stripe on the stomach.

Males sometimes have white spots on the caudal fin; they’re smaller, have a broader anal fin, and a narrower, more pointed dorsal fin.

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Breeding the Black Widow Tetra

Black widow tetras could also be spawned in teams that have a number of more males than females; they could even be spawned as pairs.

Condition all spawning fish, both the pairs or teams, with stay meals. If you shouldn’t have stay meals obtainable to you, you possibly can substitute frozen stay meals.

This species prefers to scatter their adhesive eggs amongst vegetation, so presents loads of fine-leaved crops corresponding to Java Moss or spawning mops. Keep the water temperature at 78 to 80 degrees Fahrenheit in a dimly lit tank.

Larger males usually declare a territory that they may guard throughout their spawning intervals. Once spawning has occurred, take away the parents as they may rapidly eat the eggs.

Eggs will hatch after roughly someday. Feed the fry freshly hatched brine shrimp, egg yolk, or finely ground flake meals. Black widow tetras don’t attain their sexual maturity till practically two years of age.


As with most fish, the Black Tetra is vulnerable to pores and skin flukes, parasitic infestations (protozoa, worms, and so on.), ichthyobodo an infection, parasitic infestations (protozoa, worms, and so on.), bacterial infections (common), and bacterial illness. Black Tetra are extraordinarily hardy, and illness will not be normally an issue in a well-maintained aquarium.

That being mentioned, there isn’t any assurance that you simply will not cope with health issues or illness. Remember something you add to your tank can introduce illness.

Not solely different fish however crops, substrate, and decorations can harbor bacteria. Take great care and ensure to correctly clear or quarantine something that you simply add to a longtime tank in order to not upset the stability.

A benefit of Black Tetra is that on account of their resilience, an outbreak of illness can typically be restricted to only one or a number of fishes if handled at an early stage.

When holding more delicate sorts of fish, it’s common for all fishes to be contaminated even before the first warning indicators will be observed. The finest approach to proactively stop illness is to present your Black Tetra in the correct setting and a well-balanced diet. Read more about 

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