The southern platyfish grows to a maximum overall length of 2.5 inches. Sexual dimorphism is slight, the male's caudal fin being more pointed. The anal fin of the male fish has evolved into a gonopodium, a stick-shaped organ used for reproduction. The female southern platyfish's anal fin is fan shaped. Wild varieties are drab in coloration, lacking the distinctive dark lateral line common to many Xiphophorus species. X. maculatus prefers slow-moving waters of canals, ditches, and warm springs. Omnivorous, its diet includes both plants and small crustaceans, insects, and annelid worms.