Thank you all for the advice. =) I cleaned the tank and made my roommate scrub the rocks. ;D

Tiberius is back in his tank and very pleased to have a constant heat source again.

(And the mouse is in a cage and not in my room. I never really realized how pleasant-smelling garter snakes were until I had mouse-smell in my room. Phew!)

Since I am a new snake owner, I'll probably have questions in the future, so I'll try to stick around and make myself active. ^^ Thanks for the warm welcome!