I think the key is to pick an intensity and photoperiod and stick with it so things have a chance to adapt. Err on the side of less at first. Once things are stable then slowly adjust. Height over the water is just as critical as anything else. Also depends on the corals u are keeping.
I have rapidled over a 18 gallon with 28 emitters (about twice recommended I think) on 100% for 6 hours with ramps up and down. There are 19 RB/blue, 6 white, and 3 uv. Height is 8". It's a relatively deep tank and the light is a little too much for the acros at the top but they are somewhat adapted. I am raising the fixture about half an inch every couple months and so far get better color every time I do. But need to go slow. Everything is growing well.
