N. selangoricus is most similar to N. spiniferus since it possesses acuminate scales above and below the lateral line on the caudal peduncle, a feature not shared with any other congener. It can however be distinguished by the following characters: presence of 8-12 very regular dark bars on flanks (vs. 10-13 irregularly-shaped bars in N. spiniferus), 3-5 times…

This species is the only member of the B. edithae group within the genus, and separated from all other Betta spp. by the fact that the branchiostegal membrane and posterior portion of the opercle are opaque or translucent.

The original diagnosis by Vierke also states that it has relatively small eyes and short fins with a typical pattern of partial barring.

The genus Sphaerichthys currently comprises four species with S. osphromenoides by far the best known in the hobby. It’s easily distinguishable from the congeners S. vaillanti and S. acrostoma since both exhibit a notably more elongate head and body profile, reverse sexual dimorphism (i.e. females are the more colourful/strongly-patterened), and are paternal mouthbrooders.