My fish have had 1 platy fry, 20 guppy fry, 28 molly fry, and 40+ swordtail fry. I found the platy fry purely by accident when cleaning the tank, I'm guessing he was the survivor.
I caught almost all the mollies being born on tape. All others happened when I wasn't watching. The were all born in a 10g bare tank w/sponge filter & heater with a big clump of hornwort thrown in there so the fry can hide from the mama fish.
The tank separator is a good idea as far as keeping the male/female apart, but I would go to an
LFS and get a good-sized clump of hornwort (it's cheap) and throw it in on both sides, 'cause the fry are so small right after they're born they're hard to see & easy for the big fish to eat - in fact, the only way I know when my fish dropped their babies is that they are noticeably thinner, then I have to search for the fry - always hiding in the hornwort. They feed off of it too.
It is a good idea to soak the plants in an Alum solution to kill off any hitchhiking snails/eggs and/or diseases, I read about doing that on some other thread, 3 teaspoon Alum to 1 gallon of water, soak for 3 hours.
Here I found the thread, look to the bottom
so many snails and how