Mimic,
I am following with interest on this. I have about 400 gallons in my basement all connected and flowing through an BIG Ampmaster pump with PC lighting and I have a heck of a time getting the temp down. It consistently runs around 85 F, even when ambient outdoor temps at night are getting into the 50's. I go down into the basement and it feels like a sauna. I think that it is all due to the big pump, but it surprised me as I have never had an external pump have that big of an influence on the water temp, especially with a large amount of water.
Jamison