The blue danio or Kerr's danio (Danio kerri) is a tropical fish belonging to the Danio genus in family Cyprinidae.
Originating from Southeast Asia on the islands of Langkawi and Ko Yao Yai in the Malaysian Peninsula, this fish is sometimes found in the fish-keeping hobby. It is a blue-colored, deep-bodied danio with several pinkish/gold lines from tail to gills which may or may not be continuous, over a powder blue side.
The blue danio is a peaceful, active schooling fish, so is usually kept in groups. They prefer a well-planted environment, but still need plenty of space to school. Blue danios prefer water with a 6.5 – 7.0 pH, a water hardness of 8 – 12 dGH, and a temperature range of 73 – 77°F (23–25°C).
Blue danios are egg-scatterers that spawn over coarse gravel beds. They will typically spawn at the first light of day. The eggs will hatch in about 36 hours.
The taxonomic name honors A.F.G. Kerr, who collected the first specimen on Ko Yao Yai in 1929.