Perlite and Vermiculite question..

When making a substrate for an egg tub is it better to use a mixture of both or is just perlite enough if im going to be putting the eggs on top of an egg crate and not actually in the substrate? I've seen people do both but i was wondering what everybody's opinions were on it. Any negatives to only using perlite? Any positives to mixing in the vermiculite?

I use just perlite and lots of water. the perlite is just for moving the egg boxs without having the water splash around and getting on the eggs. I know some breeders that build the egg grid up some and only use water. I build mine up some with 1/2 inch pvc pipes zip tide to the grid. lets more air around the eggs. what works well is to use glad press n' seal, no others like saran wrap. about every week peal back to check on eggs and to give them fresh air. about last 2 weeks peel a corner back just a little and keep it open slightly for air to enter the egg boxs. I do mean slightly cause of the humidity. this is when the eggs are using the most oxygen and I done this. you can add a little more water and keep your eye on the water to help with humidity. when the snakes start to brake thru the eggs I replace the press n' seal with a lid with a couple of holds in it so the snakes don't get out of the egg boxs. this egg box works really well. good luck don