The zona, also known as the red-tailed silverside, is a species of Madagascar rainbowfish. It is endemic to the Mananjary River drainage in Madagascar.
This fish species is currently threatened by habitat loss and the presence of introduced species. While it is frequently confused with the related B. madagascariensis—a common species in the aquarium trade—the two can be distinguished by specific meristics, the exact color pattern on their tail fin, and a distinct red spot on the lower jaw of breeding male B. geayi.