Humidity is a *****. I have to watch my humidity BIG time, since my setup is as follows.
Danger Den Maze 2 block
Pump / Reservoir
Big momma radaitor with 120mm fan and that part is being cooled by a 6000BTU window A/C spitting out (at time of this post 42.9F air)
When its optimal conditions, I have NO condensation, however, I was a dumbbutt and ran it the other day, right after a rain storm...and the block was wet...DOH, however, I have come up with an INGENIOUS test for condensation, I just take a rolling paper (DON'T ask...

) and swipe it across the block, since the paper is SO thin, it reacts very well with water, (by turning dark)...heehee, on a nice clear day, no probs, just gotta watch it though.