Fish referred to as G. rufa are marketed worldwide as ‘doctor fish’, with the questionable ability to remove dead and scaly skin and ease complaints such as psoriasis. These fish are quite commonly available in the aquarium trade as well, although in both cases it is unclear whether they represent G. rufa or another, related species.

Despite being a wholly unsuitable aquarium subject, C. idella is often traded as such, with an albino form having been developed specifically for the ornamental market.

Individuals which have outgrown their aquarium or pond should never be released into natural waters, either, since this species has proven capable of causing serious environmental damage under a wide range of climatic conditions.

This species has something of a confused history having been previously been considered synonymous with both A. sophiae (a separate species native to Iraq and Iran) and A. cypris (currently considered a junior synonym of A. mento). Although some populations occur close to and even sympatric with other members of the genus in Turkey phylogenetic studies have shown it to be more closely-related to the Middle Eastern species A. dispar dispar, A. d. richardsoni, A. ginaonis and A. sirhani. It's…

A 2003 phylogenetic study by Hrbek and Meyer showed that in genetic terms specimens of A. fasciatus collected from different localities do not vary as much as with other members of the genus. The latter tend to exist in geographically separated populations and exhibit localised differentiation. While A. fasciatus does show certain disparities in appearance depending on locality it is thought that periodic migration events have restricted the development of genetic diversity within the species to…

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 …