Soon.
Make sure you have lots of floating plants in the tank for her and the fry.
Don't move her into a breeding net/ trap, just leave her in the main tank. Moving her now could induce a premature birth.
And no big water changes now either, not until 1 week after she has given birth.![]()
You can let plastic plants float instead of putting them in the substrate. It does the same thing.
Try not to move the female back into a tank with males for a week after she has given birth. This will give her a chance to recover before being harassed by males. And try not to handle her with a net for a week after she has given birth. Use a net to push her towards a container and scoop her out in some water. If she is well fed she should ignore the babies![]()
Wondering if my female guppy is pregnant and what to do if she is