I have 2 of them 10-11" above my 55g breeder, maybe 12" above water surface. I also have glass lids on my tank so I know that will cut the PAR down. I keep my lights on for 13 hours a day, Blues from 9am-12pm then white/blues from 12pm-6pm then back to blues 6pm-10pm. I have the whites on 10% and the blues at 60%. Most of the threads I find on these lights are the older versions were you can change the lights by 1% and not 10%. Everyone says the older models are pretty strong. Does anyone have experience with the newer model lights? What settings do you keep them at? How is your coral growth?