hard to say exactly looks early on though if i had a guess two weeks max. There are many things people say about the gravid spot to tell when she will have the fry, but the best way is to watch for her birth canal to drop. When she is very close her tummy will go from being round and huge to being squared off if you look at it from the back. This is how you will now for sure when she is about to drop. On my female's gravid spot will change from black to red the day she has them, but all fish are different so watch for that square belly.