Taxonomy & naming
Badis autumnum was described by Valdesalici and van der Voort in 2015 from the Rathbari stream near Dinhata, in the Singimari River drainage of Cooch Behar district, West Bengal. It belongs to Badis, the genus of Asian chameleon fishes in the family Badidae, which holds many small, closely similar species from the Indian subcontinent and Southeast Asia.
Morphology
A very small fish. FishBase gives a maximum length of 1.5 in SL. Like other Badis it is stocky with a long dorsal fin and a mouth held slightly upturned, and males colour up strongly when displaying.
Habitat
The known range is the Rathbari stream in the Singimari River drainage of West Bengal, India. FishBase describes the collection site as a swamp-like area, and lists the species as freshwater and pelagic.
Feeding
Diet in the wild has not been described. Badis in general take small live invertebrates, and this species is not documented to differ.
Mating
Courtship has not been described in detail. Males defend a small territory around a cave.
Breeding
In captivity the species is a cave brooder. Males guard and fan the eggs in a cave, such as a coconut shell or a photo canister, and defend the small area around it. FishBase notes that parental care ends when the larvae reach the free-swimming stage. Clutch size is not recorded.
In the aquarium
A fish for a small, planted, quiet tank with caves, such as halved coconut shells or short lengths of pipe, and no boisterous tankmates. It is sold by specialist dealers and is best kept as a pair or small group with hiding places for each male. FishBase gives no water chemistry range, so keep it as you would other soft, slightly acidic to neutral stream Badis.
Conservation
The IUCN has not assessed Badis autumnum, as far as the atlas records. It is known from one stream drainage, which makes it vulnerable to local habitat change.