Why not just use a ceramic heater. I kept my pair of Surinam red tails in a simple 100 gallon tank. Newspaper for a substrate, and a 100 watt ceramic heater with a ceramic fixture on one side. The newspaper makes cleanup a snap. I don't know if you've kept larger snakes but when they excrete, it's not small nor does it smell good. Using a diff substrate will make cleanup a little harder. Provide the snakes with a large dog dish of fresh water and they're fine. Snakes aren't picky about living conditions. If you provide heat, food weekly until they're well grown ( then you cut them back to every other week ), and water along with a daily spraying when shedding their skin; they will thrive. Commercial substrates run you the risk of contaminating the habitat with mites which are a dangerous pest to snakes. Go simple and make it easier on you and the snake.