I'm actually using newspaper on top. I read that somewhere and it seems to be working really well. If it dries out too much, I can spray it with a water bottle without worrying about spraying the eggs. Earlier, I had tried using paper towel, but found that it fell apart too quick, into little pieces. I also like the newspaper because it's simple to just lift up quickly and check the eggs, without causing too much of a temp fluxuation. I'm sure any of the three ways work, though.