When you pt them in a separate tank is entirely up to you Benjamin. I like to guess when things are about a week away from a drop and move my fish at that time. It lets the female settle in and relax a bit if I am right and at least gives her some peace during a birth if I have waited too long. There is also a thread I have created that I called My Molly's Progress in my signature area. It is a pinned topic i the livebearer section of the forum but the idea is to help you judge just where in a fish's pregnancy your specific fish may be. What I did was to photograph my fish from one drop to the next and post lots of pictures along the way. The end result is a reference that may help you judge your own fish's progress.
