The dark male constantly follows both of them and won't leave their sides. The yellow one is almost as fat as the pregnant one. Now that I know that I have a pregnant Guppy. What do I do? How long is their pregnancy and how can I tell when its time? OH MY!!!
Pregnancy period is about a month (21-40 days) depending on the female/tank specs/stress and so on.
As for how to tell, I'm not sure from practice(mine birthed while I was asleep/not looking), but I've read to look for them being 'squared off' and for eyes of the fry in the gravid spot?
At 21 days you could also just move her to her own tank till she births and when she's done move her back, use that tank to raise the fry until they're big enough not to be eaten.
I got 12 fry, but you can expect 3 to 70, but I've seen people talk about drops of 200+.
You can feed powdered flakes, or treat them like betta fry(bbs,microworms and the like). Mine /love/ the decaps I've been feeding.
It's better to feed tiny amounts often through they day than 2-3 big meals. In a heated tank they can digest/poop in 30 minutes/an hour so I just feed my fry whenever I remember(every hour or two when I'm home/awake).
water changes~ lots of water changes.
If you won't want to keep the fry they're good as feeders to larger fish(even bettas for the first day or two if you have larger bettas).
Or you can give them to your local fish store.(some may buy them, but usually not for much).
You can also rehome them on here. ^^