ive got a fan from target about a 10in 10$ and i wedged it in the back blowing on the surface. comes on with a timer when the halides come on. i have a 75gal with 20gal sump/refug. dual 175wt halides 96wt pc actinics before fan temp at 84 now with fan 80 in the day and 78-79 at night.