I have one fan setup as they come out of the factory, But then I have another fan at the other end pulling air out.
It seems to work quite well at the moment between the 4 i'm getting around 800gh and they are running cooly.

I've added an extraction fan to the room which is then pumping the air into the coolest part of the warehouse, its a bit noisy but people are appreciating the extra heat.  The 4 ants are using about the same wattage as one of our electric heaters, so I'm basically getting paid for some of our heating bill.

Excellent today another difficulty increase :-)