LOL....talk about a blast from the past!!!
I'm kind of glad this post is a Lazarus post. At the time, I was convinced that I knew exactly how to run my new 200G SPS prop tank with all my fancy book learnin' because there should be enough C and N in my tank for sure.
I didn't have one of the more common problems with new SPS keepers which is browning out....I had the complete opposite my colors became a little less vibrant. I upped the flow a little which helped but I know this is going to sound funny but I actually needed to make my water dirtier.
I called Mojo. This was a while back so this is going to be
HIGHLY paraphrased and based on memory. He said something along the lines of, "Everyone needs to eat and you get different things from different sources. If your only source of nutrition was a salad, you would be missing some important parts of your diet. You need proteins, carbs, and fats. SPS Corals are no different. They cannot get 100% of their diet from their zoox alone, bacterioplankton alone, bacterioplankton digesting fish poop alone, etc.
Then he said something along the lines of, "With that said, when you get done eating a well balanced meal, what should you do with the 'leftovers'? Do you leave them on the table to be wasted and rot, do you throw them under the table so the kitchen looks clean and let them rot there, or do you throw them away and let them rot in the landfill?" "If your SPS are lightening up, feed them more, but make sure your system has a way of getting rid of the leftovers".
I highly suspect that if that tank had been a 75 or 90 with that light bioload, everything would have been just fine. I just had too many mouths in a 200 and I had to slowly tweak the system.