The black phantom tetra (Hyphessobrycon megalopterus) is of roughly tetragonal shape, light grey in coloring, with a black patch, surrounded by iridescent silver edging, posterior of the gills on each side. The male's fins are black, as is the female's dorsal fin; the female's pelvic, anal, and adipose fins are reddish in color. A long-finned variety, apparently developed by captive breeders, is sometimes sold. The black phantom tetra reaches a maximum overall length of approximately 4.5 cm (1.75 in).