I always take a peak by day 3, even though you really can't see anything. I usually can see by day 4 with white eggs, but not until day 7 or 8 with my medium brown eggs. It must be extremely hard to candle maran eggs, but they look so cool. It would be fun to have a couple marans. And I'm a sucker for candling, I usually end up candling everynight because it's just so cool. I know people say not to, but I have had very good hatch rates of about 90% and even a 100%, so I think it's fine.