I would prefer to have them vary in speed based on humidity. Ideally they would constantly turn at a low speed but the Profilux would increase the speed in steps as the humidity rises. For example at humidity levels of <50% constantly on at low speed (maybe 10-20% of max speed), 50-60% humidity would increase the speed to 30-50% of max speed, 60-65% humidity would increase the speed to 60-70% etc.

I understand that the Propeller Control unit is specifically for use with the GHL Propeller Breeze aquarium fan? In any case it's the same idea using a varying 0-10 voltage to change fan speeds (the propeller Control unit connects to an L port).

Or am I overthinking this and just need the ventilators to be on or off depending on humidity? My worry is that they would constantly be on full speed...