If you have a dollar store or a Big Lots(or a Walmart works too), get an inexpensive soldering wand and put some holes in the tubs. If they are 15qt tubs, I like to do 5-6 across the front/back and 7 along the long sides. This gives a good humidity range for me when the snake and waterbowl are in the tub.
Start with fewer holes though and you can make more if the humidity gets too high.