Xiphophorus

The green swordtail, Xiphophorus hellerii, is a livebearer native to southeastern Mexico, Guatemala, Belize and Honduras. Among the world's most recognisable aquarium fishes, it is ubiquitous in the trade, where selective breeding and hybridisation with X. maculatus and X. variatus have produced a bewildering array of ornamental forms. The name is often misspelled X. helleri.

The platy, Xiphophorus maculatus, is a livebearer from the Atlantic coastal plain of Mexico, Guatemala, Belize and Nicaragua. Wild fish are almost never seen in the hobby, where dozens of selectively bred varieties are available, some produced by crossing with other Xiphophorus species. Many commercially bred platies are not very hardy because of inbreeding and over-production. Very peaceful, it suits the beginner as long as the water is moderately hard or harder.

The variable platy, Xiphophorus variatus, is a livebearer native to the Atlantic slope of Mexico, with feral populations in several other countries. Most on sale are mass-produced in the Far East and Eastern Europe, and many commercially bred platies are not very hardy because of inbreeding. Wild fish are slimmer than X. maculatus with a slightly longer dorsal fin, and should be kept from crossbreeding with domestic forms. It lives in shallow, heavily vegetated streams, ponds, swamps and ditches.