Background : I found some cheap hatching eggs for sale on craigslist. I'd really like to give myself a leg up in all possible ways for the next pile of eggs that will go into the incubator, so even if I'm not spending a lot money, I'd still like the lot of them to be fertile. The seller said that he has 2 roosters to 20-30 hens. That seems like a low ratio to me. What do you guys think? For optimal fertility in hatching eggs what would be a good roostern ratio?