Instructions
Check the sex of your fish. Platies will breed without any effort by their owners. As long as there are two or three female fish to every one male fish, the fish have probably bred recently. Females are larger than males, at approximately 2.5 inches, while males are only about 1.5 inches. Males have a small fin on the underside of their abdomens toward the tail. This is used to inseminate females.
Observe the back underside of your female platy. Pregnant platies develop a small brown or black ball around their abdomens. This is the fish fries' yolk sac. This ball will grow while your fish is gravid and is a sure sign that she will have babies. In some cases, the ball may begin to change color or shrink after several weeks of consistent growth. Fish fries eat their yolk sac just before being born and a change in the ball is a good indication your female is about to give birth.
Watch for signs that your female is preparing to give birth. Females may begin behaving erratically a few hours before giving birth. Rapid darting, frequent eating, aggression and any behavior that is not typical of your fish is a sign that birth is imminent.
How to Tell If a Male & Female Platy Are Having Babies
Platies are small tropical fish that range in color from drab brown to bright orange. Unlike many other species of fish, they are live-bearers, which means that they do not lay eggs and have a period during which they are gravid -- a term for pregnancy in fish and some other animals. Because fish occasionally eat their babies, it's important to be able to predict when a fish might give birth so that the babies can be removed from the fish tank. A few simple clues indicate that a male and female platy are going to have babies.