Hey brooke, I use a 600watt HPS. And currently its about 2 feet above the plants. The fan runs at 45 mins ON 15 minutes OFF. Do you think I should have it running contstantly? Its spring here in Oz atm, so nice warm weather during the days, but gets very cold at night, and if I run the fan all night it gets down to like 62-65F. To cold thats why I leave the fan off for a while so the temperature gets a bit warmer.