Brachydanio kerri

Brachydanio kerri, commonly known as the Blue Danio or Kerr's Danio, is a small and vividly coloured species from clear hill streams on the Malay Peninsula and surrounding islands. Its most immediately striking feature is its deep, saturated sky-blue body — a more uniform and intense blue than the iridescent striping seen in most danios — with a delicate yellow or gold mid-lateral line adding a warm accent.

In the aquarium it is a peaceful, active schooling fish that behaves identically to other small danios. It does best in a group of eight or more in a planted tank with good water quality. The blue colouration is most intense in well-conditioned fish maintained in clean water with a varied diet, particularly one that includes live or frozen foods.

Despite being described in the literature since 1929, Brachydanio kerri remains less well-known in the hobby than Zebra or Pearl Danios. It deserves far wider appreciation as a beautifully coloured, easily maintained nano-community species.

Water: Temperature 22–26°C, pH 6.0–7.5, GH 5–15; clean water with regular changes is key to maintaining the vivid blue colouration. Tank: Minimum 40 L; well-planted with open mid-water swimming; gentle to moderate flow; secure lid. Feeding: Micro-pellets, flake, and frozen micro-foods; live brine shrimp and cyclops enhance the blue colouration significantly. Breeding: Egg-scatterer over fine plants; follows standard small danio breeding protocol; not frequently bred in captivity. Compatibility: Peaceful with all small community fish; excellent with Microdevario, small rasboras, CPD, and nano tetras.