Ozman, I use a 120 CFM exhaust fan out through a dryer vent. I also use a 65 pint dehumidifier. Additionally, I place glass covers on the tank at night and take them off in the am. The other thing that cuts down on humidity is not using evaporative cooling. I use a split chiller with the condensing unit outside.
I'm in the process of seeting up a large reef (240g display, 500g+ total system volume) in my basement. All tanks & equipment will be housed in a dedicated fish room with it's own HVAC. I will use a mini split (European style) A/C unit which basically puts the condenser outside. With the hot/humid summers in Michigan, the A/C will regulate room temp and consequently tank temperature. A 1hp chiller will be installed for back-up. An HRV (Heat recovery ventilator) will be vented through an existing window in the room. The HRV will exhaust humid air in the winter while retaining most of the heat. It uses internal heat exchangers to do this. If the room is still too warm in the winter (although I doubt it will be), I will add fresh air ducts to the outside with a ventilation fan in order to pull in cool air as necessary. I hope to make this as automated as possible.