I'm late to this thread but I'm growing in a exoterra 18x18x24 with high humidity and what I've learned the hard way is that mold forms when there's not enough airflow (and H is high, etc).
Find a computer fan (120mm is ideal)- I've used DELTA fan to really good effect. This sort of controller (
12V Motor Speed Controller, DROK DC Motor Driver Board for Brush Motor 7V-60V 20A 420W PWM Control 12V 24V 36V 48V Regulator Cooling Fans Dimmer Governor Pulse Width Modulator with Adjust Knob: Power Converters: Amazon.com: Industrial & Scientific) will let you adjust the speed easily.
Also, standing water puts the H at nearly 100 the entire time it's around, so that make things worse, though with a fan, I haven't noticed any trouble after a couple days but have never let go farther than that.
Linear Mode
