Platies are livebearing fish, and they breed by spawning. In spawning, male fish release gametes directly into the water near the female fish, directing the flow of gametes via their specialized anal fin. Male fish have narrow fins that help move gametes toward the inside of the female whereas female fish have broad fins. Females can store gametes within their bodies, releasing up to six broods after a single mating.
Platies breed readily if they are given enough cover in their tank to feel safe. This means planting a variety of tall aquatic plants. The vegetation provides hiding places for the tiny newborn fish.
Platy males are often aggressive, so it is recommended that females outnumber males in breeding tanks. This keeps the pressure off of females who are sometimes targeted for aggression by sexually frustrated males. It is also recommended that male fish be removed after breeding as they have a very strong reproductive drive and may continue to be aggressive to females even after spawning with them.
When females are pregnant, it is important not to stress them by moving them to another tank as this can cause them to abort spontaneously. Pregnant females also require very clean tanks, and newborn fish must be removed from the tank soon after birth to prevent other fish from eating them.