This species was known as B. sp. ‘Mandor’ or B. sp. ‘ninja’ prior to official description. It belongs to the Betta foerschi group/complex of closely-related species within the genus, of which members share the following set of characters: possession of iridescent blue or green unpaired fins; rays and interradial membranes in unpaired fins not contrasting; dorsal fin with thin, bright white distal band; opercle with two, reddish-yellow, vertical bars.

Members are regarded as being closely-related to bubble-nesting Betta species since they share exhibit certain similarities in morp…

This species is included in the Betta unimaculata complex of closely-related species within the genus, of which members share the following set of characters: body long and slender with depth at dorsal fin origin 18-25 % SL; head large and blunt with width 19-24 % SL; long maxilla and lower lip with distance from tip of lower jaw to posterior end of maxilla 27-54 % HL; caudal-fin rounded in shape, occasionally with elongated median rays; pelvic-fin short and filamentous; dorsal and anal fins relatively pointed.

Like others in the suborder Anabantoidei this species possesses an accessory breathing organ known as the labyrinth. So-called due to its maze-like structure this organ allows the fish to breathe atmospheric air to a certain extent. Comprising paired suprabranchial organs formed via expansion of the epibranchial (upper) section of the first gill arch and housed in a chamber above the gills, it contains…

This species is included in the B. pugnax complex of closely-related species within the genus, an assemblage of which members are notoriously difficult to tell apart from one another, but which can be characterised collectively by the following set of shared characters: relatively large head measuring 28-40% SL; live colouration usually brown with green or blue iridescent spots; male with similarly-coloured scales on opercle, sometimes extending to abdomen; juveniles and females usually brown with two central body stripes and a dark marking on the caudal peduncle; anal-fin in mature specimens pointed and often elongated; caudal-fin lanceolate.

This species is included in the Betta unimaculata complex of closely-related species within the genus, of which members share the following set of characters: body long and slender with depth at dorsal fin origin 18-25 % SL; head large and blunt with width 19-24 % SL; long maxilla and lower lip with distance from tip of lower jaw to posterior end of maxilla 27-54 % HL; caudal-fin rounded in shape, occasionally with elongated median rays; pelvic-fin short and filamentous; dorsal and anal fins relatively pointed.

This species was previously included in the Betta foerschi group of closely-related species within the genus, but following its redescription in 2012 now lends its name to the B. rubra group.

It was first placed into its own species group by Witte and Schmidt (1992), primarily on the basis of a triangular marking that appears below the eyes of the fish, although Tan and Ng (2005) suggested that this feature is insufficient to warrant the fo…

B. channoides and B. albimarginata together comprise the Betta albimarginata group/complex of closely-related species within the genus, these differing from all other members of the genus in colour pattern and by possession of 9-12 anal-fin spines (vs. 0-4). They look very similar to one another but differ in the following characters: anal fin spines 9-11 in B. albimarginata vs. 12 in B. channoides; anal fin rays 21-23 vs. 23-25; lateral scale rows 26-27 vs. 27.5-28; trans…

This species is often confused with B. krataios in the aquarium trade, the latter having been known as B. sp. ‘Kapuas’ prior to description. The two can easily be told apart as the caudal-fin is rounded in B. krataios but spade-shaped and in adults, highly-extended in B. dimidiata.

Together these two comprise the B. dimidiata group of closely-related species within the gen…

At one locality close to Serian, Sarawak, the habitat comprised a swiftly-flowing, clear hill stream with a substrate of quartz gravel and variably-sized rocks. The pH was 7.0 and there was no aquatic vegetation. The stream was approximately 10 metres across at its widest point and between 5-80 cm deep. B. taeniata was found in sluggish stretches among submerged tree roots, leaf litter, or overhanging riparian vegetation.

This species is included in the B. bellica group/complex of closely-related species within the genus, an assemblage of which members share the following set of characters: long and slender body with dorsal and ventral margins almost parallel; body depth 23-28 % SL; 30-33 anal-fin rays; 11-13 dorsal-fin rays; 32-34 total vertebrae; body dark brown in colour with iridescent green markings on each individual scale.