The black tetra (Gymnocorymbus ternetzi), also known as the black skirt tetra, is a popular freshwater fish from the Characidae family. Known for its striking appearance and lively behavior, this species adapts well to aquarium life and is relatively easy to breed, producing numerous offspring.
However, black tetras can sometimes nip at the fins of other fish. Because of this behavior, they are not ideal tank mates for fish with long or delicate fins. It’s best to avoid keeping them with species that have veiled or long fins to prevent any potential issues.
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Habitat in the wild
The black tetra (Gymnocorymbus ternetzi) was first described by Boulenger in 1895 and later introduced to Europe in 1933. This species served as a model for the creation of the GloFish tetra.
Native to the freshwater rivers and streams of Brazil, Paraguay, and Argentina, black skirt tetras are commonly found in the Mato Grosso, Paraguay, and Rio-Negro rivers. In their natural habitats, they prefer slow-moving or stagnant waters such as marshes and flooded areas, often in well-shaded rivers and streams. These waters are usually clear or slightly turbid, with riverbeds composed of sand, gravel, and leaf litter. This environment provides ample opportunities for the fish to explore and forage.
Despite their wild origins, black tetras have adapted well to aquarium conditions and are now widely bred in captivity. Today, most black skirt tetras found in aquariums are farm-raised, with minimal need for wild capture.
Description
Body and color
Black tetra has high and flattened body, typical tetra body structure, which is tall and laterally compressed.
The name “Black Skirt Tetra” comes from their coloration. The upper half of their body is shiny black, extending from the dorsal fin to the caudal peduncle. The lower half of their body is typically white or silver, creating a stark contrast.
It has dark-silvery coloring with three vertical black stripes. One of them crosses the eye, the second one starts at the opercles endings. The remaining part of the body starting from the third stripe, including upper and proctal fins, is black and it looks like a skirt. The pectoral, dorsal and pelvic fins are quite transparent, and its proctal fin reminds a black skirt, as we’ve mentioned earlier. Is rather energetic and active fish, it swims in schools and they often attack each other.
Size
Black skirt tetras typically reach a maximum size of about 2.5 to 3 inches (6 to 8 centimeters) in length. Males are generally slightly smaller and more slender than females. While there can be slight differences in size between individual fish and between the sexes, these variations are usually minor.
Lifespan
Black skirt tetras typically have a lifespan of about 4 to 6 years. With proper care and a well-maintained environment, some individuals may live slightly longer.
| Characteristic | Description |
|---|---|
| Scientific Name | Gymnocorymbus ternetzi |
| Common Names | Black Skirt Tetra, Black Widow Tetra |
| Size | Approximately 2.5 to 3 inches (6 to 8 centimeters) |
| Lifespan | 4 to 6 years |
| Temperament | Generally peaceful, but may nip fins if stressed |
| Schooling Behavior | Prefers to be kept in groups of at least six individuals |
| Body Coloration | Upper half is shiny black, lower half is white or silver |
| Fin Coloration | Fins are generally translucent or slightly reddish-orange |
| Natural Habitat | Freshwater rivers and streams in South America |
| Preferred Water Parameters | Temperature: 72 to 79°F (22 to 26°C), pH: 6.5 to 7.5 |
| Diet | Omnivorous – Accepts high-quality flakes or pellets, Supplement with live or frozen foods like brine shrimp or worms |
| Compatibility | Peaceful and can coexist with other community fish, Avoid aggressive or fin-nipping species |
| Breeding | Egg scatterers – Separate breeding tank with plants required |
Types of black tetras
Long Fin Black Skirt Tetra
This morph is selectively bred to have longer, more flowing fins compared to the standard black skirt tetra. While it is commonly available for purchase, its care requirements are similar to those of the classic black skirt tetra. However, breeding the long-fin variety can be more challenging due to potential inbreeding issues.
It’s important to note that the extended fins of the long-fin black skirt tetra can make them more prone to fin nipping and damage. Therefore, it is advisable to keep them with compatible, non-aggressive tank mates that won’t harm their delicate fins.
Albino black skirt tetra
The primary difference is their coloration: albino black tetras lack the pigmentation that gives the standard black skirt tetra its dark color, resulting in a pale or white appearance. Despite this difference in color, albino black tetras have the same care requirements as their non-albino counterparts.
Glofish tetra
Glofish tetra – these are genetically modified (GMO) fishes. This is a modern and very popular trend in aquarium husbandry nowadays. However, you should buy such fishes sensibly, keeping in mind that GMO have never made anyone healthier and these fishes lifespan maybe shorter due to this.
Difficulties in keeping
Black skirt tetras are an excellent choice for beginner aquarists due to their easy care and adaptability. These fish thrive in a variety of conditions and accept a wide range of foods, making them versatile and low-maintenance. They are well-suited for community tanks but should not be kept with long-finned species, as their nipping behavior can cause damage. For a harmonious aquarium, pair them with other non-aggressive fish that have similar care needs.
Care and keeping in a tank
Tank size
Given their active nature, black skirt tetras thrive best in spacious tanks. A minimum of 20 gallons (75 liters) is recommended to comfortably accommodate a school of these energetic fish. However, a larger tank offers even greater benefits. It provides ample swimming space, closely mimicking their natural habitat, and helps reduce aggression among tank mates. Additionally, a larger tank facilitates more stable water parameters and offers greater flexibility for aquascaping, enhancing both the health of the fish and the visual appeal of the aquarium.
Water parameters
The ideal temperature range for black skirt tetras is between 72 to 79°F (22 to 26°C). They thrive in slightly acidic to neutral water conditions, with a preferred pH level between 6.5 and 7.5. Maintaining stable pH levels within this range is essential for their health and well-being. Black skirt tetras are adaptable to various water hardness levels but generally prefer slightly soft to moderately hard water, aiming for a range of 5 to 15 dGH (degrees of General Hardness).
To ensure a healthy environment, perform weekly water changes of up to 25% of the total water volume and use a reliable filter. These practices help maintain stable water conditions and support the overall health of your black skirt tetras.
Decor
This kind of fish perfectly appears in a tank with natural biotope – sandy bottom, number of snags and fallen leaves on it, which make the tank water brownish and acidic. Tank maintenance is a standard one and the same as for all other fishes.
Diet
Black skirt tetras are not demanding when it comes to their diet and will thrive on a variety of foods. They accept live, frozen, and artificial feed with ease. High-quality flakes or pellets formulated for tropical fish serve as a staple part of their diet, with a preference for those that float on the water’s surface.
To provide a balanced diet and additional nutrients, supplement their meals with live or frozen foods such as brine shrimp, bloodworms, daphnia, and mosquito larvae. These treats can be offered once or twice a week to add variety and enrich their diet.
When feeding black skirt tetras, offer small portions that can be consumed within a few minutes to prevent overfeeding and maintain water quality. Monitor their feeding behavior and adjust portions as needed to ensure their well-being.
Tank mates
Fish must be kept in schools, since when it’s all alone it becomes aggressive. Remember that Black Widow Tetras are schooling fish, and it’s important to keep them in groups of at least six individuals. The larger the group, the more natural and comfortable they will feel.
It’s better not to keep it together with smaller fishes or long-finned ones. Because they will bite the latter, for example, don’t keep it with bettas or angelfish.
Due to its temperament tetra can be kept in a tank together with other small tetras, such as Neon Tetras (Paracheirodon innesi), Cardinal Tetras (Paracheirodon axelrodi), or Ember Tetras (Hyphessobrycon amandae). Keeping them in a mixed tetra community can create a visually appealing and lively aquarium. The black tetra is ideal for mixed aquarium.
| Tank Mate | Compatibility |
|---|---|
| Rummy Nose Tetras | Peaceful, compatible schooling tetra species |
| Glowlight Tetras | Peaceful, compatible schooling tetra species |
| Diamond Tetras | Peaceful, compatible schooling tetra species |
| Bleeding Heart Tetras | Peaceful, compatible schooling tetra species |
| Lemon Tetras | Peaceful, compatible schooling tetra species |
| Serpae Tetras | Can be slightly nippy, monitor compatibility |
| Black Neon Tetras | Peaceful, compatible schooling tetra species |
| Emperor Tetras | Peaceful, compatible schooling tetra species |
| Red-eye Tetras | Peaceful, compatible schooling tetra species |
Corydoras catfish species, like the Adolfoi Corydoras or Panda Corydoras (Corydoras panda), can be compatible tank mates. They are bottom-dwelling fish that help keep the substrate clean and add activity to the lower levels of the tank.
Gender differences: male vs female
Distinguishing between male and female black skirt tetras can be challenging, especially when they are young or not in breeding condition. However, there are a few subtle indicators that can help differentiate between the sexes:
Behavior: During breeding periods, males become more noticeable in their behavior. They may display more intense colors and engage in aggressive courtship rituals to attract females, including chasing and performing display behaviors.
Size: Females are generally larger and have a rounder body compared to males. Mature females may appear fuller due to their larger ovaries.
Fins: Mature males often exhibit slightly longer and more pointed dorsal fins than females. However, this difference can be subtle and varies among individuals, making it an unreliable sole indicator.
Breeding
Black skirt tetras are egg-laying fish with specific requirements for successful spawning. The ideal conditions for breeding are:
- Temperature: 25-27°C (77-81°F)
- Water Hardness: 4 dGH
- pH Level: 6.5-7.0
To breed black skirt tetras, start by setting up a spawning tank. Place the male in the tank first, and after a few hours, introduce the female. The next morning, ensure the tank is brightly lit to stimulate spawning. Both natural and artificial light can be used.
The spawning tank should have a bottom area of approximately 1500 cm² (50×30 cm) and should be equipped with Java moss or a caproic net. The net should have cells large enough for eggs to fall through but small enough to prevent the fish from eating them.
During spawning, the pair can lay between 500 and 1000 eggs. Once spawning is complete, remove the adults from the tank. The eggs will incubate for 24-36 hours before hatching into larvae. Within 3-5 days, the larvae will become free-swimming juveniles.
To feed the newly hatched juveniles, start with infusorians and rotifers. They have a better survival rate with these live foods compared to artificial feeds. As they grow, sort the juveniles by size and transfer them to different tanks to prevent cannibalism.