Longfin Blue Danio

Danio kerri, commonly known as the Blue Danio or Kerri Danio, is a small cyprinid native to Thailand, where it is found in streams, rivers, and floodplain waters within the Chao Phraya basin and nearby drainages. It inhabits clear to lightly turbid waters with moderate flow, sandy or gravel substrates, and aquatic vegetation along the margins. These environments are typically warm, well oxygenated, and seasonally variable.

Adult Danio kerri typically reaches about 1.75 to 2 inches in length. The body is slender and streamlined, with a metallic blue to blue-green base coloration that shifts in tone depending on lighting. A bright golden to yellow horizontal stripe runs along the flank, creating strong contrast against the darker body. The fins are generally clear to lightly tinted, and the overall appearance is sleek and reflective, especially in a well-lit aquarium.

A tank of at least 15 to 20 gallons is recommended for a proper group. Danio kerri is a schooling fish and should be kept in groups of six or more to display natural behavior and reduce stress. The aquarium should provide open swimming space with plants and structure along the edges. Moderate water movement is preferred, reflecting their native stream environments.

Water conditions should be stable and clean. Temperatures between 72 and 78 degrees Fahrenheit are appropriate, with a pH range of roughly 6.5 to 7.5 and soft to moderately hard water. Danio kerri is adaptable but thrives best in well-maintained aquariums with good oxygenation and regular water changes.

Feeding Danio kerri is easy. In nature they feed on insects, larvae, and small aquatic organisms. In the aquarium they readily accept flakes, micro-pellets, and frozen foods such as daphnia, cyclops, and brine shrimp. A varied diet enhances coloration and supports overall health.

Temperament is peaceful but active. Danio kerri does well with other similarly sized, non-aggressive fish that can tolerate its constant movement. Suitable tankmates include other danios, rasboras, small barbs, and peaceful bottom dwellers. Very timid fish may be stressed by their activity level.

Breeding is possible in captivity. Like other danios, they are egg scatterers that deposit eggs among fine plants or substrate. Adults do not provide parental care and may consume eggs if left in the breeding tank.

Danio kerri is a vibrant and energetic schooling fish that brings color and motion to freshwater aquariums. Its metallic blue body and contrasting yellow stripe make it a standout species for community tanks with active, similarly sized fish.