The black tetra (gymnocorymbus ternetzi) also known as the black skirt tetra, high-fin black skirt tetra, and black widow tetra, is a freshwater fish of the characin family (characidae). It is native to the paraguay and guaporé river basins of southern brazil, argentina, and bolivia. 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. It is a schooling fish, and requires at least six in a group. All speciments are packed in pressurised oxygenated double plastics bags of 10 per box. The bags are packed in polystyrolfoam boxes dimension. 75x35x40 cm.