Platy fish are natives of subtropical North and Central American freshwater. Identified since the mid 1800s (Günther 1866), they were originally classified in the scientific genus Platypoecilis, the source of the “platy” nickname. Later, they were recognized as being related to swordtails, of the genus Xiphophorus, and reclassified into that genus. However, the “platy” nickname stuck with the fish.

The difference between “platies” and “swordtails” mainly comes down to the prevalence of a “sword” on the caudal (tail) fin. Otherwise, the two types of fish differ very little in their respective species. They are capable of cross-breeding and hybrids are fairly common, both in aquariums and in the wild. Hobby aquarists may have difficulty being certain of the particular species of their platies.

Common Platy Species
Variegated/Variable Platy (X. variatus)
Southern Platy (X. maculatus)

Common Swordtail Species
Green Swordtail (X. helleri)
Marbled Swordtail (X. meyeri)
Montezuma Swordtail (X. montezumae)