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Black Widow Tetra

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Scientific Name:   Gymnocorymbus ternetzi      
Min. Tank Size:   25 gallons      
Personality:   Peaceful      
Temperature:   68-78°      
pH:   6.0-8.0/0-20°dGH      
Size:   2.5"      
Diet:   Omnivore      
Breeding:   Egglayer      


Best kept in schools with 6 or more of their own species; can be kept with other Tetras, Livebearers, Rasboras, Danios, Corydoras and Dwarf Cichlids. Black Widow Tetras can be a little "nippy", but this behavior can be minimized by keeping them in a school of at least 6 or more.

Black Widow Tetra

Often recommended to novice aquarium hobbyists, Black Widow Tetras are also called Black Tetras and Black Skirt Tetras. These fish have bodies that are typically gray in color, fading from dark gray near the tail to a lighter gray near the nose. Most specimens exhibit two vertical black bars behind the gills and black coloration on the dorsal and anal fins. Black Widow Tetras are native to the Rio Guapore and Rio Paraguay basins in Argentina, Bolivia and Brazil. These fish typically inhabit slow-moving streams, creeks and tributaries that are dense with vegetation.

Tank Set-up

Black Widow Tetras are known for being unfussy when it comes to water quality and tank decorations. These fish show best when kept in tanks with sections of dense vegetation offset by sections left open for swimming. A typical tank setup would be one that has dense planting around the back and sides with plenty of open area for swimming. Choose a dark substrate with dim lighting to complete the effect. One of the best Tetras for general community setups, Black Widow Tetras are peaceful and active. These fish get along well with most Livebearers, Rasboras, bottom dwellers and other Tetras. Because they are schooling fish, these Tetras should always be kept with at least 6 of their own species.


These Tetras are omnivorous by nature and should be fed a varied diet to promote healthy coloration. Offer Black Widow Tetras a staple diet of high-quality flakes or granules supplemented with small live and frozen foods such as Daphnia, bloodworms and brine shrimp. Feed a diet consisting of a variety of foods on a regular basis to promote the best health and coloration.


Black Widow Tetras are easy to breed in the home aquarium, though a separate breeding tank is recommended if you hope to raise any of the fry. The breeding tank should be kept at a temperature between 75 and 78 degrees Fahrenheit and it should be decorated with plenty of fine-leaved plants. To encourage spawning, raise the temperature in the breeding tank to between 82 and 86 degrees Fahrenheit. As soon as the eggs have been laid, remove the adults from the tank because they will eat them. The eggs typically hatch after 18 to 36 hours and the fry will become free swimming after a few more days.

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