Xenotoca

An incredibly hardy and adaptable species that is not so popular in the hobby as it once was, probably due to its often aggressive nature. As with other goodeids, there is less of a size difference between the sexes than in many other livebearers. This is thought to be related to the relatively primitive structure of the andropodium, as the fish tend to choose mates that are of similar size so that the sex organs are synchronised. Goodeids are unique among livebearers in that the developi...