It really depends on how cold your room is, how big the tub is and how strong the UTH is (don't forget all UTH's must be controlled by a tstat or a rheostat).
Personally for any heating concerns or advice I always go to Rich at Reptile Basics.
www.reptilebasics.com Give him the temps of the room, the size of the enclosure and all relevant info and he'll set you up with something for a reasonable price that will get you to where you need to be for your snake.
Now as far as a tub setup. You want to start small if this is a young or hatchling BP. They tend to freak out with big open spaces even in tubs so go small and provide two hides. You can ventilate the lid and sides using either a drill (careful you don't crack the tub though) or by simply melting some holes into the tub using a simple and inexpensive soldering wand. Put some holes in, set up the tub complete with substrate, UTH, full water dish, hides...but no snake. Let the tub sit for 48 hours, check your temps and humidity. Adjust the heating source and put in more vent holes if needed. Best to get all that done BEFORE putting in the snake into it's new home.
Plastic tubs tend to be very stable but you have to address the lid safety issue. Tubs have lids never meant to hold an escape artist snake so add things like big black binder clips, C clamps, bungee cords, etc. Anything more than 1/8" give and you'll have a lost snake on your hands.
Here's some pictures of various tub setups. I don't add in fake plants but feel free to if you don't mind scrubbing them often.
Simple 15 qt setup (note the use of binder clips). This is an Iris brand tub. they are my favorites since they are basically glass clear plastic which is hard to find with either Sterlite or Rubbermaid......
Typical juvi ball python in his little blue plastic cereal bowl hide.....
Big 61 qt underbed storage tub for an adult female BP. This one was setup with aspen for substrate and the two hides you see in it are heavy rubber dog dishes found at a local farmer supply store.
Very simple 31 qt setup for a yearling ball python using newspaper as a substrate and plastic bowls as hides.
Similar setup utilizing terracotta plant saucers as hides (for a much smaller snake). Note the Acu-Rite setup in this example.
A content ball python.
