Should I wash fertilized hatching eggs before incubating them?

No! Never wash fertilized eggs if you plan to incubate them. Washing eggs will remove the natural flora resulting in damage to the egg. We toss out all eggs with excessive poo, and do our best to brush off the ones with a tiny bit of poo. However, if you receive eggs with a little poo, and it bothers you, you can use a soft towel and GENTLY rub it off the egg.

Eggs will still develop with a little dirt/poo on them.

Fertilized Hatching Eggs, Wash or Not Wash?