My tank is 30 inches deep and lights are 8 inches above the water. I run them at 12k (12k you get higher par on radions than 10k) for 5 hours at 80%. In the morning, I ramp up with 12k and then 20K after the high growth period is finished for color.
I'm using a combination of what Mike Paletta and Sanjay Joshi are doing in their DSPS tanks.