HCA: Hermit Crab Association

Months prior I had a problem with my tank flooding so I emptied everything and built a false bottom. My problem is living in the desert I have a hard time keeping the humidity at safe levels even with the tank wrapped three sides around and a glass top seals it with only a gap for air to circulate. So I have to spray my tank multiple times a day. However because of that I noticed water I pooling underneath again.

Here's my question with that water pooled there I noticed my humidity was staying more constant. So would it hurt anything to just add more water underneath with a couple air hoses or submersible pimp to keep the water moving around so it doesn't get nasty? My crabs cannot get under the false bottom.

Have you checked the consistency of the sand directly above the false bottom? Even though there is space down there the sand can still become over saturated and grow bacterial blooms or suffocate molting crabs. Hermits are not smart when it comes to digging - they will burrow into unsafe wetness in an effort to get as far down as they can.