Ok I am sure most of you already know this. I can't take any credit for this either as I saw it on OG before it was closed.
Items needed:
1 2" 90 degree bend
1 60-80mm 9-12v CPU fan
1 old cell charger 9-12v output
mylar or alumminum foil
duct tape
electrical tape
wire strippers(teeth)
Black spray paint(optional)

First cut off connectors on cell charger and cpu fan and strip wires. I had three wires on the fan, yellow(+) and black (-) were the only two used. Twist wires together to test, then butt connect or twist connect the wires together and wrap in electrical tape.
Spray paint inside of 2" 90 black if you would like to help reduce light leakage.(I didn't care)
Duct tape fan to 90 making sure that fan is blowing into the 90. Wrap the whole fan part of the elbow in mylar(use dull side of alumminum) leaving bottom half unwrapped.
Trace a hole in the top of lid with the 90. Cut hole. Shove the non-fan part of the 90 in the hole and plug it in.
Total cost was $9.
This has dropped and maintained my res temps between 60-64 degrees F when temps in the box were between 76-83 degrees F.
This works due to the evaporative properties of water. Some side effects are higher humidity in grow space(good) as long as it is below 80% and having to top up more often(bad). Oh well no root rot this time.
Sorry there are no pictures. I have no digi cam.

Yeah! I read that in OverGrow a couple of months ago...

Good one on posting it here! As members will be able to search, and possibly find this solution to a semi-common problem.



-turtle420
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Welcome Burn1down from a fellow OGer. Glad you put that up I will need it come the hot temps of summer! Sorry no karma here I hope we can migrate some more of the incredible amount of lost knowledge lost with the servers of OG. Wecome again and great growing!

Greetings nutrananter and burn1down.,

I too will miss the incredible posts from overgrow. I have some threads saved I will post here. F'in government.