Black widow tetras have been a part of the hobby for several decades. Almost every store in the world will have them in stock. But how good of a pet are these fish? Should you add the black widow tetra to your community tank?
What Is The Black Widow Tetra?
The black widow tetra comes from the Paraguay River basin, in Paraguay, Argentina, and Southeastern Brazil. For a tetra, these fish are rather large, reaching up to 3 inches in length. Black widow tetras are also deep bodied fish and schooling, so they need plenty of space.
Every black widow tetra you find in stores is captive bred. So they accept flakes with relish, breed with ease, and thrive in aquarium water conditions.
Black widow tetras have a distinctive appearance. They start out light gray at the front of their bodies with iridescent scales. And then fade to black as you move towards the tail. Twin black bars on the shoulders add contrast.
Their alternative common name is the black skirt tetra, thanks to the long, skirt-like anal fin. Captive breeding efforts have also resulted in a long finned black skirt tetra, with each fin elongated.
White skirt and long finned white skirt tetras are leucistic morphs of the black widow tetra. Rather than albinos, which have red eyes instead of the black eyes of leucism.
And if you want a more colorful variety, black widow tetras also come in a glofish form. These are genetically engineered using jellyfish and coral DNA.
Glotetras fluoresce green, orange, red, or purple under normal and ultraviolet light. All black widow tetra color forms share the same care requirements.
- Common Names: Black Widow Tetra, Black Skirt Tetra, Long Finned Black Skirt Tetra, White Skirt Tetra
- Scientific Name: Gymnocorymbus ternetzi
- Origin: Paraguay River
- Length: 3 inches
- Aquarium Size: 20 gallons
- Temperament: Semi-aggressive; Schooling
- Ease of Care: Very Easy
Black Skirt Tetra Care
Black widow tetra fish are excellent beginner fish. Ideal for aquarists who have a more spacious tank and want a deep bodied fish to inhabit it.
Black Skirt Tetra Size
Black skirt tetra size is substantial; full grown fish will be 3 inches long. 2 to 2½ inches is more usual, however. 20 gallons is an absolute minimum since they are also schooling fish. And should be kept in groups of 6 or more fish. 30 gallons is more comfortable, especially if your black widow tetras end up reaching the larger end of this size spectrum.
Keeping black widow tetras in a school is important for community tank dynamics. These fish are notorious for being fin nippers.
Keeping them alone encourages this behavior since the tetras squabble with each other normally. A group of 6 or more fish will focus on each other instead of slow moving tank mates. Which means you need extra space to ensure enough room for your fish.
Plant And Substrate Choices
Black widow tetras are good choices for planted fish tanks. They are carnivorous so they won’t nip at your plant leaves. Plants also provide shade and cover, encouraging the tetras to darken their colors and be more active in the open.
In the wild these fish form schools of hundreds that swim and spawn among shoreline plants. So the more plants you add, the more comfortable your black widow tetras will be.
Floating plants are easy to care for and provide loads of benefits. They not only provide shade but also don’t need extra light or carbon dioxide since they grow right at the surface. Most also reproduce fast, locking away nitrogenous waste products in the process.
Both gravel and sand are acceptable as substrate choices. Black widow tetras don’t spend time along the bottom; they swim in the mid water region. Darting to the surface when food is available.
I do recommend a dark colored substrate to bring out deeper gray and black tones in your tetras. Pale substrates reflect light upwards, causing the fish to wash out their colors to blend in.
Water Conditions for Black Widow Tetra Fish
Black widow tetras are less fussy about water parameters than other types of tetra. They are one of the few species that will even breed in hard, alkaline water. A few others include the Buenos Aires tetra (Hyphessobrycon anisitsi) and blind cave tetra (Astyanax mexicanus).
That said, black and white tetras prefer moderate water conditions that aren’t too acidic or alkaline. A pH range of 6.0-7.5 is ideal for them and easy to achieve using treated tap water. If you intend on breeding black widow tetras then soft to moderate water hardness is best.
Aquarium salt should be used as a tonic for diseases like ich rather than a regular water addition. And even then used with care since black skirt tetras are sensitive to it.
Nitrogenous waste levels need careful monitoring; ammonia and nitrite should stay at 0 parts per million. But black widow tetras are tougher than other tetras in the presence of ammonia.
They will still stress but won’t die as fast. Nitrate levels of 10 to 20 ppm are well tolerated by them.
Black skirt tetra temperature values should fall between 70-83℉. Any higher will cause stress as these aren’t equatorial fish like other tetras.
What Do Black Widow Tetras Eat?
Black widow tetras are carnivorous fish. But they don’t eat smaller fish; instead they feed on small worms, insect larvae, water fleas, and other tiny invertebrates.
Since they are all captive bred they are used to flakes and micro pellets as food. But you need to give them variety for optimal health and to increase your chances of breeding them.
I recommend pre soaking any pellet foods since black widow tetras have small mouths. They may have trouble with pellets that are offered while still hard and dry.
Brine shrimp, blood worms, and daphnia add extra protein and carotenoids to their diet. Tubifex worms are one of their favorite foods, though offer them infrequently since they are high in fat.
Black Skirt Tetra Tank Mates
Black widow tetra tank mates need to be chosen with care. These tetras are on the larger side and may bully smaller fish.
Long finned fish like fancy guppies, bettas, and angelfish are not suitable as tank mates. Black skirt tetras are ruthless fin nippers. Keeping them in groups encourages them to focus on each other. But they may still decide to chase fish with tempting finnage.
Stick to same sized community fish that are peaceful to semi-aggressive in nature. Here are a few options to consider:
- Platies
- Severum Cichlid
- Keyhole Cichlid
- Dwarf Cichlids
- Gouramis
- Rainbowfish
- Rainbow Shark
- Giant Danios
- Barbs
- Plecostomus
Black widow tetra fish are sometimes invertebrate safe, though they may nip the antennae of large snails. Freshwater shrimp of medium to large size won’t be bothered. But smaller shrimp species like Taiwanese bee shrimp will be eaten.
Breeding The Black Widow Tetra
Black widow tetras are one of the easiest tetras to breed in captivity. They are not as fussy when it comes to water chemistry. And they have been bred in captivity for decades. As long as your nitrogenous waste levels are low and you offer a varied diet, spawning is almost inevitable.
Black Skirt Tetra Male Vs Female
One hurdle to breeding the black widow tetra is telling the sexes apart. The differences are subtle but visible. Male black skirt tetras are slimmer than females. Their anal fins are longer and their caudal (tail) fins are more forked.
Females are always chunkier than males and swell up even more when they begin producing eggs. Males will then start to compete for her attention by following her around and fighting with other males.
Spawning Black Widow Tetras
Once your black tetras are ready to spawn they will pair off and swim into dense plant growth. If you don’t have any plants, try placing some spawning mops or fake breeding grass in the tank. Spawning mops are not only easier to handle than live plants; they are simple to remove to a fry rearing tank after egg laying.
Otherwise, use bundles of live plants like guppy grass or Java moss as spawning places. Both of these plants are hardy enough to grow without any special care.
Black widow tetras are egg scatterers; they will spray eggs into plant growth, where they stick to the first thing they attach to. Since the fish provide no parental care for their young, black widow tetras are a danger to their babies.
They will even eat their eggs just hours after laying them. So as soon as you see your female is no longer pregnant, remove any plants or spawning mops with eggs attached.
The eggs take 48 hours to hatch but the fry don’t need food for another 48 hours. Once they’ve absorbed their yolk sack the fry will be light enough to free swim. Then you should offer cultured infusoria for the first week. Switching to live baby brine shrimp nauplii thereafter.
Conclusion
Black widow tetra care is as simple as it gets for a tetra. So long as you avoid extremes in chemistry or hardness they will eat well and live for up to 5 years. Make sure any tank mates you have don’t have long fins, however.
FAQs
They are semi-aggressive fish and will chase tank mates that are very small. Black widow tetras are also fin nippers; even larger fish aren’t safe from being bitten.
Black skirt tetras are a larger tetra and reach up to 3 inches long. 2 to 2½ inches is more common for this species.
Male black widow tetras have a longer anal fin than females and stronger forking to the tail fin. Males are also slimmer, though both sexes have a rounded body compared to other tetra fish.
