I bought a gelid TC 120 mm computor case fan for my cabinet. 12V, variable speed, temp. controlled.
750rpm (22C) - 1500rpm (42C) 12-25.5 db
Not installed yet so can't tell you how good it is. Has a temp probe that turns the fan on at 22C or 72 deg Farenheit at 750 rpm and ramps up to 1500 rpm at 42 deg C at which time it is only supposed to be 25.5 db loud
I bought it at NCIX but any computer store should have it.
http://www.gelidsolutions.com/produc...=5&id=27&tab=1
When I get it all together, tank and cabinet, I will tell you how it runs