Setting up a 77 gallon.

[KORBIN5895]

So I just sold one of my spare 55 gallon tanks and picked up a 77 gallon terrarium for my 4 ft boa. I am unsure how to best heat my new tank. It is 2 ft tall as opposed to the 55 which was 18 inches. The top is a metal grating but I cut some glass to cover those to retain heat and moisture. I have never had much faith in uth and can't imagine heating it with a 75 watt sunglow And a 50 watt infared. He is currently in isolation with mites and is not going into it for a week it so. Any suggestions. His favorite perch is about 14 inches off the ground so basking should be ok.