I like aspen for substrate personally. My snakes love to tunnel in it, and Thamnophis/Nerodia will usually make their own hide under their water bowl (or at least they do it frequently).
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Andy Maddox
AIM: thekingofproduct
MSN: Poloboy32486@hotmail.com
Yahoo:surfandskimtx04
Houston Herp Key
The Reptizone