I have 108 watts over my 29 gallon. They were sitting right on top of my tank until today, I finally decided to hang them. 108 watts was just a bit too much, most of the time it was fine but a big trim led to algae quick. I was wondering if it is at all possible to guess where I am at now, just for curiosity. I can't see myself going out to buy a par meter just for curiousity sake.