You may hear from John N who says he continues to change water just as usual. I've been trying to follow that advice myself, and do change water while there are eggs on the cone. The brief period of time they are uncovered does not seem to hurt them. With wigglers, I change as much as I can without uncovering them. The parents are usually pretty aggressive during this. Once they're off the cone, the parents herd and corral them and I can do a pretty complete water change. As always, careful to get consistent temp, but I start raising the hardness right away by mixing in more of my well water.