There has been some discussion over the years regarding when/if to remove eggs that are beyond their expected hatch date. Some people think it’s ok to remove nonviable eggs at any time after candling. Others think it’s best to leave things as they are until the adults lose interest. The reason behind this is if you remove them early, the adults will most likely regard this as a failure and will abandon the nest site. Me? I’m in camp #2.
18 days isn’t all that overdue if incubation was delayed and it might have been for whatever reason. I would advise waiting a few more days and see what happens.
One more thing. Sometimes you can just look at an egg and see it is bad without having to candle it. You will see a clear line of difference, with a light portion and a darker portion. That is a definite indicator.
Gin
Atlanta, GA