Yes three to four weeks depending on how warm the water is, the babies first food is the invisable micro food in the tank.
I feed all my cherries with Hikari Crab Pellets as it helps their calcium intake.... the babies try and eat it too, but as i have about 100 cherries they dont get much chance at feeding time due to their tiny size.
When they are born, mine tend to feed off micro-organisms that are found on plant leaves and any moss you have
Let us know how it goes.. the eggs usually turn darker when they are about to be let free!