I have 3 computer fans mounted in my hood. The left and right side blow out and the middle sucks in air. This creates a circular pattern around my halides. I also have a fan blowing across my ballast. This set up it keeps the tank around 80 degrees, since I have increased my photoperiod to 12 hours. I think the fans blowing across the sump will very beneficial. I will post the results on my blog. . ..