Maybe this lil' bit of history will help you.
Several years ago, when I decided to go with the original 6 bulb Tek5 fixture, T5HO lighting was fairly new. I purchased the fixture and placed it over my 75. Awhile later, I started adding SPS corals. They browned out! I was really disappointed because I'd paid a lot of money, for the fixture, hoping it would be great for SPS growth. I couldn't afford to replace it, with a MH fixture, so I figured I was stuck with brown SPS corals. During this time, my water quality tests were all perfect! Awhile later, a friend sold me a used skimmer. I had a skimmer on the 75, but not a very good one. I replaced my existing skimmer, with the one I purchased, even though it wasn't much of an upgrade. Again, during this entire time, my test kits confirmed great water quality. Low to Zero nitrates/phosphates, Ca, Alk and Mg were great and well balanced. Fast forward about a month and all of my SPS started to color up, very nicely.
Even though I thought I had great water quality, the upgraded skimmer made the difference!
A few years later and I still use T5HO. My tanks all have great skimmer and my SPS colors are incredible. In fact, my ORA Red Planet colony gets way too much light. I'm still in the process of moving it lower in the tank, to regain the green that's been lost, from too much light. The green is slowly returning, but the colony is only about 10" off of the sand bed, in a 27" deep tank. I'm planning on placing it even lower, maybe all the way to the sand bed, in the near future. I've even had Acropora tort growing, on the sand bed. It retains it bright color and grows well.
