B. macrostoma 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 traded as B. sp. ‘Kapuas’ prior to its formal description and continues to be mislabelled B. dimidiata. 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/complex of closely-related species within the genus, members of which can be characterised b…

B. ibanorum is uncommon in the hobby and is apparently more frequently fished for food than the aquarium trade. It’s included in the Betta akarensis group/complex of closely-related species within the genus, of which members share the following set of characters: possession of pre-orbital and post-orbital stripes (the post-orbital stripe is faint or interrupted in some species); chin bar present; caudal-fin lance…

The type locality is an area of permanently-flooded grassland formed by the damming of a spring for agricultural purposes. The water is only around 30cm deep, transparent and supports dense growths of aquatic plants, mostly from the family Hydrocharitaceae which includes such genera as Elodea, Egeria and Blyxa. Sympatric species included Devario sondhii, a Microrasbora very similar to M. rubescens, an undescribed Yunnanilus known to aquarists as the ‘rosy’ loach and Channa harcourtbutleri.

Due to its highly amphibious nature this must be one of the most interesting, endearing species that can be kept in aquaria. Some specimens rarely enter deep water, preferring to sit in the shallows with the body submerged and eyes protruding above the surface. Others seem to favour resting completely exposed on rocks, sand or bogwood, returning to the water periodically to wet themselves. Subdominant individuals (those that are unable to secure a favourable territory) tend to attach themselves …

B. chloropharynx is included in the Betta waseri group/complex of closely-related species within the genus, an assemblage which also includes a handful of potentially new species such as B. sp. ‘Medas’ on an unofficial basis. The easiest way to distinguish these is by examining the throat markings which vary according to species.

In this case the lighter of these form a shape that roughly resembles a horizontal figure of ei…

D. exclamatio should also have a sub-terminal mouth and lack dorsal-fin filaments but some specimens possess a terminal mouth and/or possess dorsal filaments, and one specimen also had black caudal-fin tips as typically seen in D. filamentosa, whereas the description states that the fin tips are only dusky and lack distinctive markings.

This stunning fish is one of the more sought after rays in the hobby. Taxonomically it remains unclear whether it is a geographical variant of P. leopoldi or a distinct species. It has a smaller adult size and both pups (see section above) and adults exhibit different patterning than it's relative. In P. leopoldi the light spotted markings tend to be quite large, spaced out and do not extend to the edge of the disc. In P14 they are typically much smaller, more randomly distributed and prese…

This undescribed species must rank among the most jaw-dropping freshwater fish yet seen in the hobby. A good-sized adult makes a truly incredible sight. Unfortunately due to the current ban on ray exports from Brazil it is almost unobtainable and correspondingly expensive when it is. The handful of captive-bred specimens released each year can cost up to £1000 each, and we know of only a single breeder in the UK.

The patterning of this "species" is highly variable, with…