Growing to about 6 cm (2.5 in) total length, the black tetra has a roughly tetragonal body shape and is greyish in colour, fading from light at the nose to near black at the tail. Two prominent black vertical bars appear just posterior of the gills.
G. ternetzi is commonly kept as an aquarium fish by hobbyists.
The black tetra is also known as the blackamoor, blackskirt, black widow, butterfly tetra, or petticoat tetra. The black phantom tetra, Hyphessobrycon megalopterus, is a distinct species. The black neon tetra, Hyphessobrycon herbertaxelrodi, is sometimes incorrectly called the black tetra.
References
"Gymnocorymbus ternetzi (http://www.fishbase.org/Summary/SpeciesSummary.cfm?genusname=Gymnocorymbus&speciesname=ternetzi)". FishBase. Ed. Ranier Froese and Daniel Pauly. October 2004 version. N.p.: FishBase, 2004.
"Gymnocorymbus ternetzi" (TSN 162891) (http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=162891). Integrated Taxonomic Information System. N.p.: Integrated Taxonomic Information System, 2004. Accessed on 5 December2004.
Black Skirt Tetras are commonly known as BlackTetras and Black Widow Tetras.
The Black skirt tetra has many color variations most notable are the painted varieties of blues and pinks witch are most likely artificially dyed Albino BlackTetras and should be avoided.
Gender Differences: The females of the Black Skirt Tetra are plumper and have an anal fin parallel to the second fl stripe on the body.
The BlackTetra, Black Widow, or Blackskirt Tetra is distinguished by two vertical stripes and by what appears to be overly developed dorsal and anal fins making it appear as if though it has a "skirt", with most of its mass on the bottom half of the body.
This fish is shyer and not as hardy as the BlackTetra, Black Widow, or Blackskirt Tetra.
The BlackTetra, Black Widow, or Blackskirt Tetra are egg layers.