Mold is of course more prevalent where the humidity is higher. I built my own log home with a rather unique basement.
The floor is poured concrete with a plastic vapor barrier below it, that is per code. I then put 5 coats of oil bases dry-lox on the floor. Believe it of not oil base paint is a vapor barrier. Then treated 2x4" on sides every 2' with styro insulation between them. 3/4" treated plywood floor. Walls got 3-4 coats of the same dry-lox where it meets the grounds, 2 coats above that. NOTE: dry-lox will get you high! lol. OK, 2x4" walls and more styro with sheetrock for walls. I also placed a hole in my basement wall under my porch for a wall AC unit for the basement just for cooling in summer.
My idea was to stop the humidity from the ground. I did not want a humid basement.
WELL: with all that, it still will get so humid the water pipes can drip from condensation in the summer.
Long post to say ALL basements will get humid, so I'd run a de-humidifier for almost any basement. Pick one on Craig's list or somewhere. Less humidity in the basement will even help in the cages. 20% humidity in the basement will pull some of the humidity from cages, even a tub, although slower per your tub ventilation. Small bowls was a great idea.
A dehumidifier helps lot of issues not just your cages. I personally only have an issue in the summer as my basement is part of my house. So the AC is on 72 degrees and dehumidifies for me.
Far longer than I expected, sorry, I'm rarely so wordy! 
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Thanks for reading.
Big Tom
www.HerpZillA.com