B. falx is included in the Betta picta group/complex of closely-related species within the genus, an assemblage comprising species with the following shared characters: unpaired fins rounded (anal-fin sometimes tapering to a blunt point); anal-fin rays I-III, 18-24; dark marginal band on anal and caudal fins, more pronounced in mature males; presence of pre-orbital and post-orbital stripes; presence of chin bar on throat; iridescent green, gold, or blue scales on opercle.

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.

It should be noted that not all authors consider the B. pugnax group to contain the same species, with some placed in the B. picta complex by Schindler and Schmidt (2006), for example.

B. raja can be told apart from other members of the B. pugnax group by the following characters: mature males with very long pelvic fins covering 15-23 anal-fin rays or even longer than the base of the anal-fin in some cases; anal-fin and lower caudal-fin with black marginal bands; 25-28 anal-fin rays; 30-32 lat…

T. hengeli is sometimes seen for sale with the trade name of ‘glowlight rasbora’ due to the distinctive orange patterning on the posterior part of the body but we’ve refrained from using that name here because it’s also commonly applied to Trigonopoma pauciperforatum.

It can be confused with the similar-looking T. heteromorpha and T. espei although on close inspection they’re actually quite easy to tell…

This species is also sold as the ‘redline’ rasbora which is something of a misnomer as in reality the colour of the lateral stripe that gives rise to the name can vary from deep orange to golden depending upon the collection locality of the fish as well as diet, condition, and even mood. Some specimens also have a second, darkish stripe beneath the other which seems to vary in length and intensity depending on a similar array of factors. Older fish tend to possess a greater degree of black edging to the scales, especially in the ventral portion of the body.

D. johorensis can be distinguished by the following combination of characters: 5-6 dark, lateral stripes on body in specimens larger than 40 mm; stripes immediately above and below the central stripe (stripes ‘+1’ and ‘-1’, respectively) located on scale rows +2 and -2, not touching dorsal and ventral midlines (except in some small specimens from Peninsular Malaysia); stripes broad, typically between 0.5-1 scale rows deep…

May also be seen on sale under the trade names ‘Bala shark’ or ‘tricolor shark minnow’ and perhaps among the most commonly-encountered ornamental fish species. It is unfortunate that the vast majority of those traded are juveniles and tend to come supplied with little to no information provided regarding their potential size and requirements, a fairly ironic situation given the apparently precarious status of wild populations.

This species is arguably one of the most misunderstood in the hobby since it's wholly unsuitable for smaller aquaria despite its ubiquitous availability. Most retailers sell it without providing what should be considered essential information regarding long-term care and most specimens undoubtedly fail to reach their potential in captivity. The purchase of a group is also a considerable investment given that if properly cared for typical life span is in excess…

C. oblongus is another name widely misused in the trade but that species has seemingly never been exported and was described as a blueish fish with yellow fins. It’s native to streams of Gunung Salak mountain in Bogor Regency, West Java, Indonesia where collecting of ornamental fishes is almost non-existent. Other species of laterally-striped Crossocheilus also exist and may be available from time-to-time but are more easily told apart from the group described above.

One of four similar-looking, laterally-striped ‘Puntius‘ spp. native to Southeastern Asia alongside ‘P.‘ gemellus, ‘P.‘ johorensis, and ‘P.‘ trifasciatus. Of these ‘P.‘ lineatus is most often confused with ‘P.‘ johorensis by virtue of the fact that these two seem most common in the aquarium trade.

Telling them apart is relatively simple since ‘P.‘ lineatus has 0 – 1 pairs of barbels (vs. 2 pairs in the other three species), juv…