What is "rainbowfish"

n. A small colourful freshwater fish of northern and eastern Australia and New Guinea and the Southeast Asian islands.

The rainbowfish are a family (Melanotaeniidae) of small, colourful, freshwater fish found in northern and eastern Australia, New Guinea, islands in Cenderawasih Bay, and the Raja Ampat Islands in Indonesia.

The largest rainbowfish genus, Melanotaenia, derives from the ancient Greek melano (black) and taenia (banded). Translated, it means "black-banded", and is a reference to the often striking lateral black bands that run along the bodies of those in the Melanotaenia genus.