You really really really need to do something about that humidity... 23% is asking for an RI... if your tight on cash... 10$ for a 66qt tub thats pretty much the same dimensions as that 20 gallon... You can either cough up 10$ for a tub... and your humidity will be MUCH better... or you can wait till your snake gets an RI then needs to go to the vet which can cost up to 100$ easily pending the vet... Save the time and the money... pick up a tub... Also Im curious as to how you got 83 ambient temps... 90 on the hot side... but you got a cold spot of 73?