A 125 sounds pretty big. That's the size of my Oscar cichlid tank, and I could stretch out in there as if it were a bathtub, it's so long!
How big is your BP? That tank may be a bit too big, as they like a smaller, more secure tank when young. It might be a cool tank for when your snake gets bigger, and you could put a bunch of plants and different hides in therre to take up room.
I'd probably start out with a 20-g tank for now. Or better yet, look into getting a rubbermaid. It's easier to maintain humidity and good temperatures with a rubbermaid.