I bought a bag of Calcined clay. Its clay pots crushed up and fired at 1800 degrees i think but not 100% sure on the refiring temps.
Anyways its the best hatching substrate ive ever used. Ive used it for geckos and snakes and i wont use anything else.
I found it online at a bonzi tree store. Got a 5 pound bag for a few bucks.
Its light tan when dry and dark brown when wet. So its easy to learn the moisture content just playing around with it.