The medication you are using will offer instructions. Those are not mere suggestions. :) If you are not using a med, still continue with the salt at the level it is at and doing extra partial water changes for at least another week.

Depending upon the treatment, 4 days to two weeks may be the period. You need to get all (or as many as possible) of the free swimmers. They will hatch out at different times over a week. In the responses to the Ich questions in The Immediate Help section, you will find great comments by Jbo and PeterW (in a couple of places.)

Bythe way, you fry probably will be ok. It is remotely possible that they took some of the Ich with them. More possible is that one's hands, the siphon tube, a turkey baster or water container can convey some of those wee beasties to the fry tank. Be careful. Watch them. Care for the tank with any illness after caring for the other. :)