Doesn't the swamp cooler humidify by itself?
Well in that case I guess a large pond fogger and a large tub of water is your cheapest option. Or you could get a massive fogging system. Ask Andrew about that.
EDIT: There are certainly cheaper ones, but this is what I'm talking about http://www.amazon.com/Alpine-FG202L...8&qid=1354421101&sr=8-10&keywords=pond+fogger
Exactly. What I would is buy a five dollar sterilite tub at Wal-Mart, cut a hole in it' duct the fog where you need, and stick the logger in there.big you get a large tub I bet it could hold 50 gallons easily.
Maybe something like this? http://www.bigfogg.com/corral-cooler-misters.html
I guess you'd have to use an RO system?
The thing is, it has to be about 1.5" under the surface and no deeper. I have long, flat, clear containers that hold about 15 gallons and they are 7" deep, so the 2.5" fogger plus 1.5" would mean 4" or so of water I could put in there, so about 8 gallons in the reservoir.
Do you think if I put it on the floor of the greenhouse on the bottom that it would raise the humidity for the entire GH? Or maybe I should just do a small container like you suggested and put it right under the swamp cooler so that the humidity gets blown around.
You can buy ultrasonic units like that that float. They keep themselves at the right level in the water no matter the depth.
What kind of water will you use and how will you position the tube?