Taxonomy & naming
Hamilton described the species in 1822 as Labrus badis, and it is the type species of Badis. For a long time several look-alike fishes from across South Asia were filed under the name. Kullander and Britz revised the genus in 2002 and restricted Badis badis to the Ganges and neighbouring drainages, so older aquarium reports may refer to other Badis or Dario species. Pairs sold as 'Badis badis' are usually this species or a close relative, and the Catalog of Fishes name is the one to trust for identification.
Morphology
A small, deep-bodied perch with a long dorsal fin and a rounded tail. Colour changes with mood and sex, and the males show blue, red and dark barring when displaying; hence the name chameleon fish. FishBase gives a maximum length of 3 in TL, and notes that figures of up to 3 in in some publications are exaggerated.
Habitat
The species lives in rivers, ponds and ditches, and also in swamps, according to FishBase. It is found singly rather than in schools. FishBase gives a temperature range of 14 to 30 C, a pH of 6 to 8 and a hardness of 5 to 19 dH. The type locality is a small tributary in the Ganges drainage of West Bengal, India.
Feeding
FishBase records worms, crustaceans and insects in the diet. In captivity it takes live foods such as daphnia, bloodworm and mosquito larvae, and many individuals learn to accept frozen foods. Dry foods are often refused.
Mating
FishBase notes distinct pairing with an embrace, which is the courtship posture of the badids. The male displays in his strongest colours at a cave or crevice that he has chosen as a spawning site.
Breeding
FishBase gives a clutch of 30 to 100 eggs. In aquaria the species spawns in caves, with the male guarding the eggs and the newly hatched young. A small flowerpot, coconut half or length of tube is enough shelter for a pair.
In the aquarium
A good fish for a small, planted tank of 10 US gal or more with soft lighting and hiding places. It is peaceful toward other species but males squabble over caves, so keep one male with several females or give each male his own territory. Feed live and frozen foods, and avoid fast, boisterous tank mates that take food first.
Conservation
The IUCN Red List classes Badis badis as Least Concern, last assessed in March 2010. It is widespread in the Ganges and Brahmaputra lowlands and is collected for the aquarium trade.