I use a small heat lamp to keep my ambient temps up but had a heck of a time with them till I treated the top as per this thread
http://ball-pythons.net/forums/showt...highlight=tank
I would also cover 3 sides with foil as well and be sure you UTH is on a Tstat they can get hot enuff to burn your new snake. Most everyone here use this Acu-rite thermometer available from wal-mart
http://www.bing.com/shopping/acu-rit...M=EGCA&lppc=16
hope this help you out