What is your male to female ratio? And how big is your tank?
If you want some fry to survive, the best thing is to add plenty of hiding places to the main tank. Fine leaved, live plants that reach to the surface are best.
We do not, ever, recommend the use of breeding boxes or nets; they are too small for the mother fish to feel comfortable (which can lead to her aborting the fry) and too small for the fry to grow properly.