Taxonomy & naming
Hamilton described the species in 1822 as Cichla dario, from the Brahmaputra drainage of Assam. It is the type species of Dario, a genus of miniature badids split from Badis by Kullander and Britz in 2002. The name Dario comes from a local word, and the species is often sold simply as the scarlet badis or the dario.
Morphology
One of the smallest fishes kept in aquaria. FishBase gives a maximum of 0.5 in SL. Males are bright red with darker vertical bands and fin edges; females are paler and duller.
Habitat
FishBase describes a benthopelagic freshwater fish living at 0–3 ft depth. One collection site was a stream 7–16 ft wide and 12–27.5 in deep, with crystal clear water around 26 C, a bottom of sand and fine gravel, and dense growth of Limnophila, Hygrophila, Vallisneria, Ottelia and Rotala. The species is recorded from India.
Feeding
Wild diet is not described in the FishBase entry. In aquaria it takes live foods small enough for its mouth, such as baby brine shrimp, microworms and daphnia.
Mating
Males hold small territories among plants and display to females with spread fins and intense colour.
Breeding
Breeding behaviour in captivity is not recorded in the FishBase entry. Aquarists generally report that small pairs spawn among fine plants or in caves, and that the fry need infusoria-sized food.
In the aquarium
Keep it in a small, heavily planted, calm tank with cool to moderate temperatures and no larger or boisterous tankmates, which will outcompete it at feeding time. Live and frozen foods are accepted; dry foods are often ignored. FishBase gives no water chemistry range for the species.
Conservation
The IUCN assessed Dario dario as Data Deficient in 2010. Its stream habitat in the Brahmaputra system is subject to local change.