I am having a canopy built tomorrow for my 72 running 2 250W halides. I don't use a chiller and don't plan on it. Thus far i've gotten away with keeping pretty stables temps by using a fan over the sump and over the surface of the water. I am going to have a large hole drilled in each side of the canopy for fans. Can anyone suggest a set of fans to purchase (locally hopefully) and maybe give me some pointers on what size to buy, how to wire them (I am assuming the most affordable route is going to be computer fans), and other heat issues that may arise with the addition of a canopy over a tank that has always been an open top.