Matt Clarke on a tiny and colourful cyprinid that's rarely seen for sale in the shops.
Scientific name: Sundadanio axelrodi 'blue'
Origin: Indonesia - Sumatra, Bangka and around the Anjungan and Kapuas drainage in Borneo.
Size: Tiny, just 2-3cm/
3/4"-11/3" at most.
Diet: Small zooplankton, such as Daphnia and Cyclops.
Water: Very sensitive. Ideally, needs an RO-based softwater system pH 5.0-7.0.
Aquarium: This quiet, delicate species needs to be housed in a shoal with small placid fishes - other small rasboras are ideal. Plant heavily and add plenty of bushy plants.
Notes: This is currently the only known Sundadanio. Not much is known about the relationships of the genus to other fishes, but they're currently grouped with danionins and microrasboras. Interestingly, it's said to make squeaking noises when disturbed.
Similar species: This species was described in 1976 as Rasbora axelrodi. There are at least two different colour forms including red, blue and green. The blue and green forms are similar, but the red one looks more different. These morphs may be distinct species. The red one is said to come from Anjungan in western Borneo, while the bluish forms are said to be from Riau, Sumatra.
Identification: Sundadanio lack barbels and a lateral line. The anal fin should have five branched rays.
Sexing: Depends on the race, but males are more colourful, usually with more blue on the flanks and darker anal and ventral fins. These are often reddish in males, but black in females.
Breeding: No published reports of aquarium spawnings as yet.