Spectrum chart for the CREE XR-E, 5000K was chosen because of the increased yellow/red spectrum needed for photosynthesis. However I tried keeping some purple acros under pure 15watts of CREE XR-E 5000K and failed, the acros bleached and recede slowly over 3 weeks.
I have now increased to 40watts of royal blue and 15watts of white, only 1 side of the tank is lit due to the costs of luxeons USD$23+ each!