If your female guppy is pregnant, her body may look boxy or stuffed and even lumpy. She may grow even rounder as she gets closer to birthing her young. [1] X Research source You may want to use a magnifying glass to get a better look at your guppy’s shape, size, and coloring as it swims around in its tank.
Keep in mind that spotting a lot of bright colors and patterns on your guppy is not a sure fire way to identify it as male. Some types of guppies have females who are also quite colorful, so you may want to use other physical markers to determine the sex of your guppy in addition to coloring. [3] X Research source You can look at different breeds of guppies online to determine what breed your guppy is as well as the different coloring and patterns on your breed’s tail. [4] X Research source
A pregnant female guppy’s gravid spot will get darker and bigger as she gets closer to delivering her young. As her due date approaches, you may be able to actually see the babies inside her, close to her gravid spot. Once she has her babies, her gravid spot will get lighter and then darken again when she gets pregnant again.
In contrast, a female guppy will have a shorter anal fin that appears triangular in shape. Her gravid spot will be located right above her anal fin.
