Galaxy rasbora

The celestial pearl danio, also known as the galaxy rasbora, is a tiny, vividly patterned cyprinid from the small, shallow ponds of eastern Myanmar. Despite its 'rasbora' trade name, it was scientifically described as Danio margaritatus and has since been reclassified by some authorities as Celestichthys margaritatus. First appearing in the hobby in 2006, it caused immediate excitement among aquarists. Males are adorned with a deep blue-black body covered in bright golden pearly spots, with vivid red-orange fins. Females are more subtly coloured but still attractive.

At just 21 mm in maximum recorded length, the celestial pearl danio is among the smallest aquarium fish. Despite its tiny size, it needs more space than expected — a tank with base dimensions of at least 45 cm x 30 cm is recommended due to the territorial behaviour of dominant males. The ideal setup is a heavily planted aquarium with a dark substrate and gentle filtration; an air-powered sponge filter works well. Unlike many small species, driftwood and leaf litter are best avoided, as the tannins they release are not a feature of its natural waters.

Celestial pearl danios are peaceful but males can be combative with each other, so a well-planted tank with broken lines of sight is essential. They do best in groups that visually diffuse male aggression. In the wild they feed on small invertebrates and algae. In the aquarium they accept suitably sized dried foods but thrive on daily offerings of live and frozen fare such as Daphnia and Artemia. They rarely rise to the surface, so floating foods are ineffective. This species was first bred in captivity by hobbyists within weeks of its introduction to the trade.