DrZy,
I have a JBJ Artica Nano chiller that can drop a 40 gallon tank 8 degrees below ambient temperature.
I also have another suggestion that I think you should investigate for your whole home, not just the area w/ your tank.
Radient Barrier.
it's installed on the inside of your attic, and is sort of like a thin layer of tinfoil. My parents have this installed in their attic and I have stored a christmas tree shaped candel out there in their attic for 5 years and it has never once melted. When I go into their attic I am always amazed at how cool it is, nothing like the sweltering inferno that was the attic in the house I grew up in.
it could end up saving you a lot of money if you have it installed in the roof over the entire house. (lowers your cooling costs)
"Maybe in order to understand mankind, we have to look at the word itself: "Mankind". Basically, it's made up of two separate words - "mank" and "ind". What do these words mean ? It's a mystery, and that's why so is mankind." ~ Jack Handey