Sexual differentiation is usually well defined not only by coloration (more intense in the male) but also by the size and shape of the fins. The male has the dorsal fin most pigmented in black while the female has no black coloration at the base of the fin. A black rhombus spot located behind the operculums distinguishes the male. This spot is usually absent, or may be inconspicuous, in specimens bred in captivity.
Live in South America They extend from the Amazon to the middle Paraná at the height of San Pedro (Province of Buenos Aires), including Paraguay, Bolivia and the Pantanal area of Mato Grosso. On the Argentine side it is found along the rivers Paraguay and Paraná, Pilcomayo, Bermejo and streams and tributaries.