If you want to keep the genetics pure, you would have to isolate, but why bother unless you plan to sell either chicks or fertilized eggs and need to definitively state which variety they are. Even so, if you can settle for keeping just one of the varieties true to breed, just don’t allow any hens from the other to brood. As Mr Douglas stated, if you keep more than one rooster, the potential for fights arises if they’re confined together, but if you grow your flock, and they have plenty of room, a few roosters will learn to survive together, with the younger, older, and weaker ones eventually running away at the sight of the dominate one. The blood spots that occassionally form inside of the eggs have nothing to do with being fertilized or not. I’ve had really good luck with Orpingtons, and I also like Ameraucanas for their blue eggs and their uncanny ability to survive. They seem to avoid the foxes, coyotes, and hawks better than many other breeds.