[smellsfishy]

the second best i've tried so far. other than humidity increaseing fans.
Geo-thermal loop baried about 2 1/2-3' down, just under 300' of 3/4" hose in a figure8 type configureation, in a 50' area. It produces a steady, respectful 1.5-2 degree drop from input to output with a 9.5 mag (900gph). slower flow will produce lower temps and running intermitant on/off, which allows for more cooling time in ground, will drop over 10c on startup.
drawbacks.
manual labor "ouch" i used a spade, advice is get your utility marked out on your property and rent a trench digger.
As the ground warms up the drop temps will reduce.
The more pipe in the ground the more time it has to cool however once the ground around the pipe warms the transfer drops.
Slower flow means more drop but will reduce the amount of tank temp drop.
in the summer the ground will warm up thus lowering the amouint of cooling, I expect this system will rock inn the winter.
In the winter the ground will freeze thus increaseing the risk of cracked pipes and fitting and since the water goes into/out of the sump, well enough said. Insulate all pipes out of the ground, probably not the best idea if you live in saskatchewan or praireies, i grewup there i know how cold it can get.
The calculation of size of tank, hose needed, average ground temps, etc. is mind boggling.
my system is a 180g upstairs/ 1400 watts MH/150g sump in basement /4600gph closed loop/5800gph return/external diy skimmer with mag 3600 recirculating dual beckets/no chiller/ lots of fans,geo-thermal aand it holds at 81 degrees max but expect it to not be enough mid-summer.

On my list of to do's. just completed increase to a 150g sump which not only eliminated micro bubbles but stabalizes temp up/downs, and puts more water in a cooler area helping more.
ventilation fan in the fishroom/half-basement.