Black Skirt Tetra: Information and Owner’s Guide

Tetras are some of the best schooling fish for community tanks and there are many different kinds.

The Black Skirt Tetra is a particularly elegant example. They are named after their spectacular trailing black anal fin that looks like a skirt.

It gets along well in most communities and its insatiable curiosity and energy will bring any tank to life.

If you love Tetras, this is one of the best specimens to look into.

Keep reading to learn more about them including care, breeding and much more…

Black Skirt Tetra

What is a Black Skirt Tetra?

Black Skirt Tetra Close Up

The Black Skirt Tetra (Gymnocorymbus ternetzi) is a small black-and-silver fish from the Characidae family.

They are also known as Black Tetras, Black Widow Tetras, Petticoat Tetras, and Black Moor Tetras.

You will find them in slow moving streams in Brazil, Bolivia, and Paraguay, and they are most well known because of their appearance and tendency to nip fins.

When kept in an aquarium most Tetras will live for 3 to 5 years, however their iconic black skirt only lasts for about a year. As the fish ages their color will fade away and remain a pale grey for the rest of their life.

For the most part they are peaceful and perfectly sociable with others. They cannot live alone so you will need to purchase a minimum of 5. Just remember that they love to nip and pick at the fins of long finned fish.

Although they may not be as common as Neon Tetras or Cardinals, recently their popularity has been increasing.

They are usually sold in groups of 5 for about $2-$5 per group.

Key Facts:

  • Experience Required: None.
  • Nicknames: Black Tetra, Black Widow Tetra, Petticoat Tetra, Black Moor Tetra.
  • Color Forms: Silver and black, or albino.
  • Size: 3 inches.
  • Tank Size: Minimum 15+ gallon.
  • Tank Temperature: 70-85°F.

Are Black Skirt Tetras Fin Nippers?

Black Skirt Tetras are fin nippers.

These feisty fish will shamelessly pick at the fins of Gouramis, Guppies, Bettas, and Angelfish.

Males will also nip at each other’s fins when they are in competition for mates or territory.

To reduce their fin nipping you should keep an even number of fish in your school.

Pros and Cons


  • Active and fun to watch.
  • Can be kept in small tanks.
  • Does not need much equipment.
  • Very unique and noticeable appearance.


  • Loses color over time.
  • A well known fin nipper.
  • Can show territorial behavior.

Black Skirt Tetra Appearance

Albino Black Skirt Tetras
Albino Black Skirt Tetras

This fish is named after its jet black anal fin.

Its dorsal fin is also black and trails behind the fish like a long black gown. Other fins include a pair of pectoral fins, a forked caudal fin, and a tiny pelvic fin and secondary dorsal fin. In total there are 7 fins on this fish.

However after they reach a year old their iconic black anal fin begins to fade to gray.

Their body has four short black bands over a silver base color. In some cases their entire abdominal area is black to match the anal fin. This fades as the fish gets older.

However you can also find White Skirt Tetras. They are an albino Black Skirt Tetra specially bred through crossbreeding. They are completely white with colorless fins. Sometimes people inject them with dye to color them red, yellow, blue, green, or pink. Dyeing the fish shortens its lifespan significantly, so it is not recommended to purchase one of these.

You can also find Long Skirt Tetras too.

Unlike other Tetras (which have bullet shaped bodies), Black Skirts have a wide build with a thin snout and tail. There is a slight hump at the dorsal fin. Both the unusual body shape and the trailing fins contribute to its slow movement compared to other Tetra species.

Some individuals have a triangular silhouette, accented by a tall dorsal fin and wide pectoral fins. Others have a wide shape with a short dorsal fin and tucked pectoral fins.

Males have thin dorsal fins and are a slightly paler color than females. Unlike most fish, it is the females that have the most striking colors.

Growth Rate and Size

A juvenile in a pet store will usually be around 1 to 1.5 inches long.

At one year old they will reach their full size of 3 inches.

5 Fun Facts About Black Skirt Tetras

  1. These fish are related to the ferocious Piranha! They all belong to the same order: Characiformes.
  2. The colors of this fish are not related to breeding or attracting mates, but to their age.
  3. People inject them with dye to create artificial colors. The ethics of Glofish are still up for debate, but dyeing Tetras is proven to shorten their lifespan and reduce their quality of life.
  4. You can no longer find wild caught specimens in the pet trade. Every Black Skirt that you see for sale has been bred in captivity.
  5. Despite their size they are quite bold and will often take on larger fish.

Habitat and Aquarium Set Up

Gymnocorymbus ternetzi

This species is native to the Guaporé and La Plata river basins in South America.

It stays in the slow moving areas in shallow creeks and streams. They are very active and love to explore, so they will gravitate to areas with wide open space. It does not like very crowded areas or narrow spaces, but does like to shelter in caves.

Areas with low light and floating plants will often be filled with schools of these fish. They enjoy exploring caves and other hiding places and will often take shelter behind tall stalks.

To make your Black Skirt feel at home you will need to keep them in at least a 15 gallon aquarium. This tank will hold a school of 5 Tetras – each additional Black Skirt Tetra will need an additional 3 gallons.

  • Temperature: 70-85°F
  • pH: 6.0-8.0
  • Water hardness: 5-18 dGH
  • Substrate: Dark colored gravel or sand

Keep the water level low to mimic a shallow stream and do not fill the tank completely.

For this setup you should use a sponge filter to generate very little flow.

The water must be pristine at all times with absolutely no cloudiness or presence of waste products. Plant decay and rotting wood should be removed as soon as it appears.

Black Skirt Tetras prefer dim light and will become anxious if the intensity is too bright.

Do not go over about 2 watts per gallon.

For decorations they prefer areas for them to hide out in. Flowerpots and hollow logs make great artificial caves. You can also use driftwood shelves, tunnels, or stone arches. Either way only place decorations in the background or along the edges, to give them plenty of space to swim.

Plants should also be restricted to the background and the edges.

They love floating plants the most.

Float Anacharis and Brazilian Pennywort along the surface of the water. Below the surface you can plant Anubias, Amazon Swords, Cryptocorynes, Micro Swords, and Pygmy Chain Swords.

Owner’s Guide

Black Skirt Tetras

Although these fish have a short lifespan they are also quite hardy!

They are great for beginners and experts alike, but they are not good for anyone who does not want to spend a lot of time cleaning the tank.

Black Skirt Tetras require clear water and will need a 25 to 50% water change every week. Your water should be checked for ammonia, nitrates, and other waste products on a weekly basis too. Remember that waste can also be introduced by rotting food or plant decay.

Vacuuming the substrate is part of the weekly cleaning process as detritus that is caught in the substrate can rot and collect bacteria.

The filter should be checked frequently to make sure it is working too.

Perhaps the most common disease that affects these fish is dropsy. The telltale signs are a swollen belly and protruding, pinecone-like scales.

Dropsy is only a symptom of the infection, not the infection itself. Once an infection progresses to dropsy it is extremely hard to treat and can cause death.

It is important to stop infections before they progress.

Keep the tank clean, make sure the filter is working, and watch for lethargy, pale coloration, and uncoordinated swimming.

If you notice any discoloration or white spots on one of the fish in your school then you should isolate it from the rest of the school and get it medical care as soon as possible.

Feeding and Diet

The Black Skirt Tetra is a micro predator.

They eat the tiniest aquatic prey including: water fleas and other freshwater zooplankton, insect larvae, microworms, and phytoplankton.

They also nibble on plants and algae on occasion.

Most of the food Black Skirt Tetras eat cannot be seen by the naked eye!

In the aquarium their diet should be made up of fish flakes. The flakes should be about 75% veggie and 25% protein, with no fillers or additives.

Live prey should be given only 2 or 3 times per week.

You can offer daphnia, mosquito larvae, larval brine shrimp, tubifex, and microworms. As a treat you can give them frozen or dried worms and frozen insect larvae. You may also want to give them powdered algae wafers or spirulina as a supplement.

Every so often you may spot your fish nibbling on the leaves and stems of your plants – they will not eat enough to cause any significant damage.

Fish flakes should be given once a day every day.

You may want to crush the flakes into powder to make them easier for the fish to eat.

Meals should only be large enough for the entire school to finish in under 5 minutes. Never leave food lying around or it will rot and attract harmful bacteria to the tank.


These fish are extremely inquisitive and social.

They are very bold for such small fish and are always interested in what is going on.

Black Skirt Tetras can be found at the middle levels of the tank and usually hide behind tall plants. They will interact with each other, similar-sized fish, and even some larger fish.

However, there will be times when Black Skirt Tetras prefer to stay out of the way. When this happens they will choose a plant or a cave to hide in. If the light is low then they will be active for most of the day. Higher light intensities will make them more anxious and compel them stay hidden.

Most of the time these fish will be perfectly sociable however during mating small conflicts are to be expected.

Tank Mates

Despite their reputation as a fin nipper these fish are perfect for community tanks!

In the wild they would be found alongside other Tetras, Cyprinids, and even predatory Piranhas! Of course, not everything that they live with in the wild is a suitable tank mate.

You should focus on Nano fish like Danios and other Tetras. The Zebra, Giant, and Celestial Pearl Danios will all fit in well. Neon, Cardinal, and Ember Tetras are all good picks.

Harlequin, Lambchop, and Clown Rasboras will add a dash of bright color providing a contrast to their black and grey colors.

Livebearing fish like Platys and colorful Swordtails will also add quite a bit of life.

Kuhli Loaches, Cory and Oto Catfish, and Bristlenose Plecos are all good additions too.

While most Cichlids are out of the question, the Bolivian Ram and African Kribensis are peaceful enough.

Snails and shrimp of any kind are safe for this tank. Try including Panda Bee Shrimp for a great color. Nerite and Malaysian Trumpet Snails for algae cleaning.

You should avoid all long finned fish such as Bettas and most other Gouramis. These shameless little nippers will not be able to resist picking at their fins. Convict Cichlids, Jack Dempseys, and other aggressive Cichlids should be kept away as well. Even the Angelfish is a bit too aggressive for these fish to handle.

Of course you should never include predatory fish or fish that are large enough to make a meal of your Tetras.

Keeping Black Skirt Tetra Together

These schooling fish cannot survive on their own.

They must be kept in groups of at least 5.

If the group size is smaller than 5 they will be very aggressive to each other.

They will also behave quite badly if there are too many males in the group. The female to male ratio should be 2:1 to keep the peace.

Typically they stay in a group, but an individual may wander off every so often.

Black Skirt Tetras Mating

How To Breed Black Skirt Tetras

Breeding these small fish is not too difficult.

In fact it often happens on its own without any external help!

You can start by setting up a 10 gallon breeding tank, with a sponge filter and a water temperature of 77°F.

When a male is interested in a female he will begin to chase her around the tank. He will also behave more aggressively to the other males. The male and the female will pair off and swim side by side within the school – this is when you can place them into the breeding tank.

To get the couple into spawning condition you should feed them bloodworms and other protein rich foods 3 times a day. A male in breeding condition will have tiny white spots appear near his caudal fin and the female will get rounder.

Females can lay up to 1000 eggs per spawn. The male will fertilize them externally which turns the egg from white to clear. You can use a breeding brush to collect the eggs at the bottom of the breeding tank.

Once the eggs are fertilized the parents must be removed immediately as they are notorious brood cannibals.

It will take around 2 days for the eggs to hatch.

At this point the larvae will survive off of their yolk sacs for another 2 days.

You can start by feeding them infusoria and after 2 weeks you can introduce insect and brine shrimp larvae to their diet. This will be their primary food source until they develop their colors.

Once your Black Skirt Tetras develop their black skirts they are ready to join the community tank.

Black Skirt Tetra History and First Sighting

The Black Skirt Tetra was discovered by George Albert Boulenger in 1895.

It was first classified as Tetragonopterus ternetzi.

However once the Gymnocorymbus genus was classified in 1908, the species was moved from Tetragonopterus to Gymnocorymbus.

It entered the aquarium trade in the 1950s and was introduced to areas outside of its range as a result. Escapees from aquariums were discovered in Thailand and Hong Kong. However, since they cannot survive for very long outside of their range the species is not considered an invasive species.

Captive breeding began in the 1980s which eliminated the need to harvest the fish from the wild.

Now, it is exclusively captive bred in the pet trade.

Every so often a few specimens will escape from a fish farm and end up in local streams and tributaries, but they have never established a viable population outside of their native habitat.

Compared to other Tetra species the Black Skirt is quite uncommon. However it enjoys a following among community tank enthusiasts.


Black Skirt Tetra
Other Common Names: Black Tetra, Black Widow Tetra, Petticoat Tetra, Black Moor Tetra
Scientific Name: Gymnocorymbus ternetzi
Family Name: Characidae
Distribution: South America
Size: 3 inches
Color: Silver and black, albino
Care Level: Easy
Temperament: Semi aggressive
Lifespan: 3-5 years
Minimum Tank Size: 15 gallons
Tank Mate Compatibility: Peaceful community fish

The elegant Black Skirt Tetra is both beautiful and manageable. They are a wonderful freshwater fish.

However, if you do not like to spend a lot of time cleaning then this is not the right fish for you. It needs weekly maintenance and water changes, and its water must be crystal clear.

The opportunity to admire its beauty is worth the little bit of work though!

There are so many things to love about this tantalizing Tetra. Because it moves slowly, it is able to draw more attention than its swift swimming cousins. Its inquisitive and active behavior makes it quite entertaining to watch.

In a colorful and wellkept aquascape it will surely shine.

What sort of community do your Black Skirt Tetras live in? Let us know in the comments section below…