Little sun is able to penetrate the forest floor so aquatic habitats are shaded and water temperature may be relatively cool, while conductivity and hardness are generally low and pH slightly acid. Macrophytes are uncommon though there may be dense, marginal vegetation, sometimes overhanging the full width of the stream, the roots of which may penetrate the banks underwater. Typical substrates are sandy but covered by a layer of leaf litter with fallen twigs and branches.

As of 2006 only 4.6% of the old forest was left with the remainder existing only in small, highly-fragmented patches, most covering areas less than 10 km², of which some are now officially-protected reserves. Kottawa Forest is one of these and comprises just 15-20 hectares of wet, evergreen jungle, though the combined Kottawa-Kombala forest covers around 1600 ha. A number of minor, pristine streams…

Wild swordtails are a fairly basic green colur. However the vast majority of swordtails available in the hobby today are hybrids of X.helleri with X.maculatus or X.variatus. There are a huge number of selectively-bred varieties available, including wagtail, lyretail, tuxedo, albino, neon, red, green and hi-fin.

Swordtails may undergo what appears to be a change in sex. In young fish this may simply be late development. However some adult females develop male characteristics which is thought …

Wild examples are rarely-seen in the aquarium hobby although selectively-bred ornamental strains are widely-available for which care is identical.

These are normally traded as ‘red’ or ‘yellow’ chromide and have a solid yellow-orange colour pattern with no dark elements.

It exhibits a widespread sympatry with the con…

This species is euryhaline and mostly inhabits brackish estuaries, coastal lagoons and the lower reaches of rivers.

It also occurs in freshwater habitats, however, including a number of inland lakes in Sri Lanka although it appears to have been introduced intentionally.

This species isn't especially popular in the aquarium trade but is undoubtedly interesting despite its lack of colour. In addition to its survival ability in the absence of water it's also capable of producing audible sounds though the purpose of these has not been fully-studied. Naturally-occurring xanthic and albino forms have also been recorded.

There is considerable confusion as to the taxonomic status of the two species currently occupying this genus, with ichthyologists widely…

Generally considered to have an enormous natural range extending from Iran to Taiwan and Bali, with records existing from Iran, Iraq, Afghanistan, Pakistan, Nepal, India, Sri Lanka, Bangladesh, Bhutan, China, Myanmar, Thailand, Laos, Cambodia, Vietnam, Malaysia, Indonesia, and Singapore.

However there exists significant evidence to suggest that C. gachua as currently understood represents a complex of similar-looking species, and a taxonomic review of the group is clearly required.

Endemic to southwestern Sri Lanka where it appears restricted to the so-called ‘wet zone’ (see ‘Habitat’).

Confirmed localities are all within the Bentota and Kelani river systems and Kottawa Forest Reserve in Galle district, Southern Province.

Type locality is given simply as ‘Habitat in India orientale’ and this appears to have caused confusion regarding the species’ distribution with it of…

This species is also referred to as ‘Kretser’s paradisefish’ and ‘spotted gourami’.

There exist three colour forms, two of which exhibit a greater degree of reddish or violet pigmentation in the fins, respectively. The third is more bluish and was described as M. kretseri minor by Deraniyagala (1958).

This species is also traded/referred to by the vernacular name 'Ceylon fighting fish'. It differs from its only congener, B. hasselti, by its overall reddish (vs. brownish-grey) body colouration, and absence (vs. presence) of a mosaic-like patterning in the unpaired fins.

At least three putative phenotypes have been recorded. The nominative, and commonest, mostly inhabits clear streams in rainier zones…