Frequently, when purchasing guppies for the first time, often the buyers are told the females are pregnant. I believe, the store clerks are simply informing the buyers that females weren't seperated at birth from the males, which leads the females being pregnant at the time of purchase, whereas if the females were seperated from the males, they wouldn't be pregnant.

So, what do you check for? Her "gravid spot" will grow large and darken as the fertilized eggs develop. Closer to delivery time, the spot will be nearly black. Some say they are even able to see the developed babies within the gravid spot, but I can't say I have seen this.

Often times, when delivery is near, the female will be having difficulties swimming due the weight of the developing fry. I don't always notice this problem, but it should be something you watch for on a daily basis.

The female will try to find a hiding place, being it behind plants in the tank or often times, my females hang out near the heater. They just seem to want to be left alone for delivery time and don't want to be bothered especially by the frisky males.

What are the symptoms of delivery? The most noticeable thing the females do which I spot immediately, is they refuse to eat. This is MY indication the females will be delivering soon. If you watch them daily at feeding times, you should be able to notice which fish isn't eating. Then you know the babies will soon be delivered. Although some females may take in food, which appears they are eating, but keep watching to be certain they don't spit the food out of their mouths.
Other symptoms are brilliant, vibrant, colors in the female, or pacing up and down the sides of the tank. Hiding near a heater or in plants. Perhaps even sitting on the bottom. A female may even have her head pointed down and tail pointed up in attempts to deliver. The belly of the female will become "squared", meaning as the birthing canal drops into place it will have a protrusion from the gravid spot giving the appearance her belly has squared off.

The next thing you should do is have a breeding tank or net set in the main aquarium. Actually, I suggest you have two available. One for the female giving birth, a second for the fry. Some of the breeder tanks come with a divider section to separate the birthing female from her fry, but the fry don't necessarily stay in the section they're meant to be in which will lead to the female eating the fry after she delivers the last baby. So, if you're able to, seperate the fry from the female, and separate the female from the other fish.

Leave the female in her breeding tank, anywhere from 24-48 hours after delivery so she may rest awhile before being released into the main tank to be harrased by the males. Make certain you also feed her after delivery as she will be extremely hungry.

After placing any female into the breeder box, and she doesn't deliver within 24 hours, you ought to consider releasing her back into the main tank. Keeping a fish confind to small quarters for greater than 2 days won't help the fish. It can be compared to human females being put on bedrest to stop premature delivery of infant children. So, understand, guppy females need to have excercise to assist in the maturation of the fry. If you believe the female is too large to release and fear her safety, place her near the heater, and you may even want to increase the temperature of the tank to help with the maturation process of the babies and help the female deliver. But again, don't leave her in a breeding tank for any undo length of time. After delivery, reduce the temperature back to what it was if you had increased the temp.

How long should delivery last? Delivery time actually depends on many environmental factors. On average the fry are delivered in 4-6 hours. If delivery is difficult, it could take up to 12 hours to deliver all the fry. It also isn't uncommon for a stressed female to release a couple fry one day, then stop delivery. Perhaps then a week later she will complete delivering all her fry.

Mark the date of delivery on a calendar. You should begin rechecking the female after 25 days for signs of delivering fry once again. Depending on the temperature of the tank, the female can reproduce every 25-90 days. Generally, the higher the temperature, the faster the rate the female matures the eggs.

How many fry should you expect? First delivers for a young mother, on average are between 8 and 25 fry. Subsequent delivers can range from 25 to 50 fry. As the female matures, the batch of fry can range from 40 to 100 in healthy females. This is why they are termed the million's fish.