A 30 Gallon Breeder would be 36" x 18" x 12". I've never heard of a 35 Gallon.
Some may say that vivariums or glass tanks are too stressful for a bp. There is a whole debate on it somewhere on here. It's a bit lengthy.
http://ball-pythons.net/forums/showt...ight=tank+size
I figure as long as you have enough hides and ground cover your good to go.