1. Larger belly: The female guppy's belly will become noticeably larger and rounder as the pregnancy progresses.
2. Darker gravid spot: The gravid spot, which is a dark patch on the female's belly, will become more prominent and darker as the birth approaches.
3. Behavior changes: The female may become less active and spend more time hiding or staying close to the bottom of the tank.
4. Chasing: The female may chase other fish away from her, especially if they come close to her belly.
5. Restlessness: The female may swim around the tank restlessly, searching for a suitable place to give birth.
6. Breathing changes: The female's breathing may become more rapid or labored as the birth approaches.
When you observe a combination of these signs, it's likely that the female guppy is about to give birth. It's important to provide a safe and comfortable environment for the female during this time, such as a breeding tank or a separate area with plenty of hiding places.