I just posted this in response to another post, but I believe you may use the same, as your depth in the tank is not that much. I would raise the light tell you get a nice full spread and start there.
Well it not the easiest question to answer. I believe a lot of it depends on the height of the lights, because the closer you have them the more focused they seem to get and as you raise them they start to lose that focus and par drop drops because it has increased its spread. I have tried many different and found what works for me the best is 14" above water at a higher intensity 10 hrs. 75% Intensity and 45% Color. With a start of 0 and 5 rises to 40 and 25 in a 1/2 hr then goes to peak, same for Sunset is the same just reverse. For yourself with a Nano I would try the 14 " at 50 Intensity and 45 Color for now as you have no SPS. You sort of can tell when things are too much, your Color on the Corals will start to get a White wash look to them as you add the Intensity and you don't want that. I hope this may be of some help. But observation and slow adjustments are the best way.