Great suggestions here for how to clean your tank.

But, on a different note, why do you want to keep a BP in a 75 gal tank? It's going to be very hard to heat properly, and keeping the correct humidity level will be a nightmare. Not to mention that a 75 gal is waaaay to big for a young BP, and probably overkill for a full sized adult.

Just wondering if you've really done the reseach or are just using this tank because it's what you have on hand?

If you want use this 75 gal as a display tank, I urge you to look into corn or milk snakes. You may find yourself disapointed with the display qualities of a ball python.