http://www.reptiledepot.com/substrate.html
25 quart bag $12.99 and i use 1/2 a bag plus half a coconut husk brick that goes for $3.49
but yes i do use a thermostat but i also use a thermostat on my 20 the only things that i added to my 70 that i didnt have to on my 20 are 2 extra feet of flexwatt and piece of 1/8 inch plastic that i cut to cover the screened top of the cage thinking bout it now i only spent $10 extra there. clearly i had to buy the cage but i was talking bout the heating and humidity aspect of it all i only spent 10-15 more