So I recently moved my boa to a bigger tub and decided to use a mixed substrate using about 60- 70% organic coconut coir, 40% play sand and only 10% spagnum moss. However his humidity has been staying between 75 and 80 and one morning I woke up and it was at 89. His tub has 4 3 inch vents on them. I have bought 4 more and am waiting for them to arrive but what I've been doing is leaving the lid completely open while I'm home so I can make sure he doesn't escape but even then his humidity is 75 to 80. What else can I do to lower it and will he be ok? He's only been in with the new substrate for about 3 days or so. He was on paper towels for 3 days before I switched to the substrate mix. I've also tried keeping a fan on but I'm worried it will make his enclosure too cold. I only started using the fan for a few minutes a day to avoid his enclosure getting too cold.