Based on behaviourial and morphological characters and details of head and body patterns, Witte&
Schmidt (1992) have classified betta fighting fishes
into 15 species groups (see also tan & ng, 2005),
one of which is the Betta splendensgroup. The term
species group is used here for an assemblage of species sharing diagnostic characters. Members of the B.
splendensgroup are bubble-nest building bettas with
the following characters: small head, often brightly
coloured body, iris of eye with iridescent green or
blue patches, body slender, head with parallel opercles
when viewed dorsally, red or brown anal and caudal
fin rays contrasting with iridescent interradial membrane (especially in male) (Witte& Schmidt, 1992)