How can I tell my guppy is pregnant

21–30 days Guppy. Guppies are highly prolific livebearers giving birth to between five and 30 fry, though under extreme circumstances, she may give birth to only one or two or over 100. The gestation period of a guppy is typically 21–30 days, but can vary considerably. (source)
https://www.youtube.com/watch?v=dg1PV6zzTu4
As your female fish becomes pregnant, she will grow a bulge at the back of her abdomen. This typically appears over the course of 20-40 days. Does your fish have a red or black spot? Sometimes, when a female fish is pregnant, she will develop a “gravid spot” on the abdomen. Jul 27, 2017 (source)
https://www.youtube.com/watch?v=CzR_sfcK5sM
Once you’re able to tell that the female guppy fish is pregnant, consider moving her to a separate breeding tank. This isn’t a requirement, but it can make a huge difference. Being separated from the rest of the fish will reduce stress tremendously. Furthermore, it’ll give the babies a fighting chance at survival. Jun 11, 2021 (source)
It is not normal for guppies to lay on the bottom of the tank. In my experience, there are a number of reasons guppies lay on the bottom of the tank and these include illness, stress, and poor water quality. Pregnant females may also lay on the bottom of the tank prior to giving birth. (source)
Delivery Time. It is recommended that a pregnant guppy be removed from the community tank, or isolated in a part of it, in order to give birth to her fry. (source)
The swimming up and down the glass in a pregnant guppy is a typical sign of giving birth thumbs2: When a female gives birth she releases a hormone which supresses the eating of the babies for 6 hours… so once they are born you have 6 hours the time to get them safe or add some moss etc. where they can hide in. Mar 4, 2008 (source)
https://www.youtube.com/watch?v=eAbwqvHsG8Y
60 days Usually, the gestation period lasts for 60 days. However, they can fertilize the eggs multiple times, because they store the sperm from the male for months. A Molly can give birth to many new young fish (10 – 60 at a time). (source)
A female guppy can have 50-60 young at one time. When Mother Nature sees such a large family, she knows that the fish tank is overcrowded. May 29, 2022 (source)