Make sure you get a variable voltage DC power supply so you can fine tune the fan speed and noise, much better than constant speed. You will find in winter months you can slow them down by switching to 10.5 or even 9v and it cust down on evaporation and the heater kicking on to compensate for overcooling. I paid $5 at Harbor Freight but have seen them for less that $10 at Wal Mart and other places, some have molex connectors but its no big deal if they don't, its only two wires to cut and twist, butt splice or solder together.