Well i have a 1kw and a 177 cfm inline fan pulling the exhaust air from the hood. It works great but I wouldn't dare run it w/out the fan. I doubt you'd need that much for a 250....but you'll definitely need something. You should look into cool tubes if you don't have a reflector already. Those things rock and you can get them pretty close to your plants for better results.
Weedhound Reviewed by Weedhound on . NEEEEEED HID OPINION! Ok here is the deal.....below is a picture of my 3' tall cabinet and the 250w hps system i am considering buying...I have this idea where what i will do is cut a square in the top of the cabinet so that my HPS reflector can fit snug right over the hole....the ballast will be at the top of the closet on a shelf about 3 feet above the growbox....i have two fans 120mm computer fans already installed in the box one at the base of the plants and the other at the top of the box....not comming out the Rating: 5