While not the most colorful of the poeciliines, Knife Livebearer makes a dazzling display when kept in a shoal. The “knife” consists of a series of scales on the lower edge of the body located between the vent and the beginning of the caudal fin. Alfaro huberi (Orange Rocket) from Guatemala, Honduras, and Nicaragua has a central body spot, is smaller (around 2 3/4in/7cm), and is less frequently available.
[Ebook] Encyclopedia of Aquarium & Pond Fish – David Alderton (Photo by Max Gibbs)
The knife livebearer has two rows of scales along the lower edge of the caudal peduncle which look like the blade of a knife. Pale in colour, the iridescent sheen on the bodies of healthy fishes makes them well worth keeping. Males grow to about 5 cm (2 in) and females 7.5 cm (3 in)
[Ebook] The New Guide to Aquarium Fish – A comprehensive and authoritative guide to tropical freshwater, brackish, and marine fishes – Mary Bailey – Gina Sandford