My guppy is having fry, she's in a breeder box but fry keep swimming back up through the griddle and mumma fish is eating them... Only managed to save 3 so far when they swim back up and putting them in breeder net :-(
Try putting a few pebbles on the bottom then grind up some fry food and let it sink 2 the bottom near the rocks so they will b more encline
I used to have those breeder things, but was terrible at guessing when mom would drop the fry.
What I have now is an area of my tank with a lot of Christmas moss growing, with a short plant growing nearby. I have a never ending supply of fry and I don't have to do a thing about it.
Hopefully this helps for the future.