What spectrum are you running?... you may need more white to get an adequate PAR level. I'm running 5 Primes, on my 22" deep tank, with great growth from SPS etc. I run 1ok starting at noon and ramping up to 100% by 4:00pm. It continues to run 10k at 100% until 5:00pm and then switches over to 100% 13.5k from 5:00 - 8:00.... then ramps down 13.5K until my moonlight kicks in at midnight.
I would be more than happy to run some PAR tests on mine, if needed, for you. Just let me know what spectrum, percentage, distance BWL and the distance the fixtures are AWL on your setup and Ill run some tests.
IMG_4539 by
Toby Broadfield, on Flickr
I'm already seeing some growth on this Aussie Slimer and I have had this frag for less than 2 weeks.
IMG_4629 by
Toby Broadfield, on Flickr