Very interesting discussion. This is something I have been researching for awhile. now. I remember not that long ago, reading the Tank of the Month over on Reef Central. There were some amazing SPS dominated tanks, and every single one of them would say their NO3 and PO4 are at zero. Now it doesn't seem to be possible to grow coral with out higher levels of Nitrates. Unless using Zeovit which was not around at the time. So what changed?