I had D120s for months cranked up to 100% blue and 75% white. I borrowed a friend's PAR meter and found out that some were getting 800+ at the top of the tank and the sand was getting 300+. I have since dialed them down so that the top of the tank is getting 600 and the sand/frag rack is getting no more than 200. Since then I have seen them opening up. Some of the ones that were thriving in uber light (700+) were my Orange Bam Bams and Tubbs blues. The Candy Apple Reds were in high light and they have noticibably gotten smaller and have not popped out any new polyps. All the frags on the rack have started looking better after I lowered the light (rastas, sunny ds, super saiyans, hornets, etc). I would definitely counsel buying or borrowing a PAR meter because you can't just "eyeball" it.