One device in my op that I haven't said quite enough about is the dehumidifier. Just a little 400 watt unit, but it takes about 10 litres of water per day out of the air.
Before I had the dehumidifier, powdery mildew was killing my leaves as fast as I could grow them and the really big, heavy nice colas got grey mould (bud rot). This all despite a really serious 8" axial blower sucking air out of the room and a pair of 6" axials pulling air in.
I've had this particular dehumidifier in service for about 4-5 years now. It started leaking some water a few weeks ago, so I took it out of the room to tear it apart and fix it. Slacker that I am, I didn't get to the job right away- 2 weeks went by.
Guess what came back? You betcha, powdery mildew and grey mould destroying my buds. Little fungus fuckwits. Humidity had been hovering at 65-70% without the dehumidifier. They reckoned that was as good as an engraved invitation.
So... I fixed the dehumidifier. Some internal rust was causing water to drip outside the drip tray. Cleaned up the rust with Mr Dremel and put some silicone sealant in a few places. Working like a charm again, no leaks... but I suspect the steel frame which holds the condensation coils is gonna rust out in a couple more years.
The fun part was that humidity dropped from 65-70% to 40-50%. Otta sort out the fungi.