The amount of moisture I can pull from the air is much greater then the evaporation rate that takes place. If you tried using a small dehumidifier then yes all it would do is actually heat up your room and have no affect on relative humidity.I don't mean to get off topic but, Isn't a dehumidifier in a fish room kind of a waste? Their job is to pull moisture from the air so with a bunch of tanks, it's not going to dry air and going to suck up a ton of electricity. Excuse my ignorance but am I missing something?