400W MH/HPS with cooling tube

I set up my new 400w light and intake fan last night. The exhaust does wonders for the temp in my tent!! Right now i have a MH bulb in and have it about 15 inches from my plants. It seems like i could get much closer to the plants with the cooling tube keeping the heat from the light down. Should i move it closer or keep it between 12 - 18 inches away?

I have a 400w MH in a 6" cooltube, I can get close as hell. Both in the vertical and horizontal. Right now (verticle) I have plants 4"-6" away from the tube, they love it!

Thats what i was thinking too. Im using a 6 inch cooling tube with a powerful exhaust so im going to move it closer tonight. Thanks

I have a 600w cool tube and I had it about 10" away from two week seedlings and it started bleaching them out, so just be careful and watch out for that when the lower the light...

8-12" on two 1000 watt, air cooled hoods....

8-10" away from my plants is usually the distance I leave my lights w/ my cool tube. Before I got my cool tube I never let it get closer then 12" and they seemed to do alright under it with a fan blowing on the light.