The diamond tetra, Moenkhausia pittieri, is a small freshwater fish of the characin family (family Characidae) of order Characiformes. It is found in and around Lake Valencia in Venezuela, South America. This species exhibits clear sexual dimorphism, with males having much longer dorsal fins than the females. Males also tend to be more brightly coloured, but both sexes are attractive fish and have become popular with aquarists. The dorsal and anal fins are purple and the body is silver. The eye is marked with red above the pupil, and there is a dark band running along the midline of the body. Their common name comes from the bright, iridescent scales along the flanks.