second link in my sig...

I have a 400w hps with a cooltube, tube fan and carbon filter, with both 10cm and 12.5cm tubing. You will see in my log that I changed the setup many times until I finally have it right this time. Temps are 26-28 C...

I actually have my thermometer sitting on top of the cooltube. If you have the proper reflectors for the top of the cooltube, it will stay nice and cool up there:thumbsup: