Thanks man. I actually don't have a CO2 meter. I was hoping to get one for the next run. The regulator I have is set on a slow leak when the lights are on. I'm shooting for 1500ppm but I don't actually know for sure. I think my ac is wasting some. I'll buy one of those one time use testers before I raise the temp. I guess my main question is; which will yeild better? Right now they appear to be on pace for a very nice yeild. That is why I am very reluctant to change anything. But when I read the FAQ I got the impression that the heat would actually increase the yeild. What do you think? Have you tried it both ways? I just moved and set up a new room and I'm way overbudget. I can't afford to screw this one up. What should I do? Thanks again for the help.