I have done this in 2 enclosures Lynn. I really didn't notice much difference. I know it is forcing air in and causing exchange. I was plannkng on ddoing the same on the mantella tank, except i was planning on using one of my 2 port pumps and push air from both sides. Although i don't need to be as concerned about humidity as you do. Let me know how it works out for you.

Btw.....see any new growth from the moss spores yet?