You will know by day 8 usually. If you cannot tell for sure, then wait longer. Use the sniff test though. There is a distinct odor to rotten eggs.![]()
That

Next eggs I am hatching are gonna be light colored eggs. These beautiful, dark, opaque eggies are rather a mystery. Kinda pointless to try to candle. I guess new years will be either a happy surprise or a "learning experience" I am going to go stare at the incubator and think "grow, grow, little chickies" because that's about all I can do. . .
Stay away from blue, too, then lol. You'd think blue, being a light color, would be easy to see through but gosh darnit, I've had better luck seeing into black eggs than blue.