I was reading this interesting thread recently:
"the secret to colorful,healthy corals....obvious to some,elusive to many"
http://www.reefcentral.com/forums/sh...8#post24694998
and the oft quoted "one should have at least barely detectable NO3 and P04 to have colorful corals' came up and it got me thinking since I very rarely have any detectable nitrate or inorganic phosphate readings (ELOS, Salifert). Yet. coloration is quite okay, me thinks:
So I sent a water sample to Triton and they gave my the big 'Yellow' warning sign that PO4 was only at 0.0015, so half of the 'desired' level.
Since my system falls outside the current 'norm', the obvious thing to do was look at what was different between a typical reef tank of today (skimmer, GAC, GFO, etc.) and a system that doesn't use all these filtration products.
I think the main important difference is that the free-living bacterial count in an unskimmed/no GAC tank is much higher (~10X according to Ken Felderman's research as well as POM and DOM are around 2-3x higher). In my mind, the relative abundance of these nutrient sources in a 'naturally filtered' tank could explain why untectable NO3 and PO4 levels can still produce nicely colored corals.