Well, when I was tossing my bator together and using whatever was laying around out of desperation, I ended up using chicken scratch grain to fill the bottom of the bator. I'm stuck on the idea of having a "substrate" on the bottom to help keep temps stable (it really seems to be working). BUT, I have a problem. I'm making a seperate hatcher, but I'm wondering, how do I keep everything sterile? I'm probably going to switch the scratch grain out and put sand in later (probably after the first batch hatches, and then just toss the grain outside for the birds), and I can bleach the sand and rinse it out every once in awhile, but, I'd like to figure out a way that I can have my sand and not have to sanitize it after every use. Any ideas? I was thinking about using the towel/cheese cloth method that I asked about earlier, and just placing that on top of the sand, but just wondering if anyone else has any bright ideas. And, just an FYI, my heat source will always be from the bottom (I just think it's more effective this way.) So the heat radiates up through the sand/grain to the eggs, keeping the top and bottom nice and warm (top from the air temperature).