Ongoing issue with keeping sand moist?

[happyhermies33]

So i had been working on my tank upgrade which is a150 gallon ReptiZoo front opening terrarium and i’ve made it almost completely airtight (plexiglass on the mesh lid, plastic wrap covering any other opening and covering the small gaps where the doors slide). the first time i mixed up my substrate i accidentally got my ratio wrong and added to much sand and it ended up being almost completely dry. so i went Petco and picked up some EcoEarth bricks and broke them apart with 1 gallon of water. i discarded some of the original sub because it had too much sand to EE and then added the very moist EE to what was left of the sand in my tank. the texture was a perfect sand castle consistency so i put all my decor back in and it’s been a few weeks now and the top layer (about 1- 1 1/2 inch deep) is dry again. is this normal for a large tank? underneath the top layer is still very moist and even leaves a little condensation on the glass. do you think the middle to bottom layer is moist enough for them to molt? or should i completely redo it again but with 50/50 playsand to EE? they have dug a few burrows that look like they held the shape but i’m not sure if the top layer drying out is normal for a large tank. also my heat mat is above the sub so i’m not sure why is drying out, does anyone else have this problem? my heat and humidity stays at 80 degrees and 75-80% humidity

[HermitGuy3]

I have heard that it is normal for the top layer of substrate to be dry and the rest to be moist. Maybe you should spray it a little? I am fairly new to crabbing and only have a 10 gal though, so maybe wait for someone more experienced to come along.

[Mrmickey]

It’s normal for the top to be dry; the moisture is usually deeper. Maybe try a light mist. I recently bought a similar product from https://www.dealsandstealstoday.com/, and I noticed the same thing the top layer looked dry, but the moisture was locked in underneath. A quick spray helped even things out!