The data in http://www.plantedtank.net/forums/sh...d.php?t=189944
show that you would get medium light, around 45-50 micromols of PAR, with that light on a standard 75 gallon tank. Last week I measured the PAR from a 16 inch long RayII light, and the readings were very close to what is in that thread, including the spread of the light. I think those are superb lights for getting good uniform light over a very large area. And, don't forget some light will be reflected off the front and back glass down to the substrate, so you should get even more PAR than the data show.