I just installed 3 250 watt MH's in my canopy and i had a huge concern about the heating issue. What i did was to install 1 coralife 4" fan at each outer corner on the ends of the canopy. At that point i went to Home Depot and purchased 3 screened vents like what you would see under the eves of a house and cut holes in the rear and installed them . I cut one hole towards each end and one right in the middle on the back. This in turn draws air from the rear of the canopy and pulls it past each bulb towards the front outer corners. I didnt have a single degree temp change from this set up . I hope this helps someone in the future and can post pics if anyone needs them.