CoolTube size for 1000w

I have a 6" cool tube with a 600w and a 400cfm fan. Grow room is expanding and I got my hand on a nice 1000w ballast for nothing. Will the 6" tube be OK or is it too close to the bulb?. Do I need 8"

If the bulb fits in the tube, it'll work. You're fans cooling capacity will be your limit. You'll be, at least, 8-10" further away with the 1000, than what you were with the 600, so the heat at the canopy shouldn't change all that much, assuming the rest of your environment is setup right.

i think it will work on a 6 inch tube, but i personally would spend the 60 or 70 bucks for an 8 inch tube. i think your light will run cooler, which will = longer life.