Instructions
Determine the female platy. The female platy's body is thicker than the male and will have a wide fin behind the belly. Male platys have a long fin under their stomach area, called a gonopodium, which is the breeding tube for a male platy.
Inspect the female's anal fin. When female platys are pregnant, they will have a dark spot near the anal fin. Seeing the dark (gravid) spot is more difficult with darker colored female platys because their color will sometimes blend with the spot.
Observe the female's belly. Another indicator of a pregnant platy is that her belly will grow large.
How to Tell If a Red Tail Platty Is Pregnant?
The platy is a popular freshwater aquarium fish because of its mild personality and hardiness, which makes them good for beginners, according to Tropical Fish and Aquariums. Platys come in color variations of yellow, orange and red; the red tail platy is just a red platy with an yellowish colored tail. Platys, along with swordtails, mollies and guppies are in the livebearer class, which means they don't lay eggs but instead give birth to live babies. Platys are easy to breed and telling when a female is pregnant is not difficult.