Wondered if you'd catch that
On the topic of nitrate and phosphate, I've been unable to obtain a reading in my 12g from either (Salifert test kits) for over 2 years, even though I have two adult, messy Clownfish and I feed the LPS in the tank weekly. Being a living system, I know that these substances are available and that the water column concentrations are lower than what can be detected by the kits. While I am actually not after good growth, it still happens due largely to the fishes' waste products.
Here's where I'm going with this. We have systems where these nutrient substances are testing '0'...and the corals are thriving. We have other systems with somewhat elevated levels, and the corals are also thriving. This leads me to believe that the key is in understanding what is actually available and assimilated by the corals at any given point in time and how that might effect their vitality.
For example, if I feed my fish moderately 3x/day I am supplying
bursts of nutrients every 3-4 hours, but I do not detect these bursts as elevated phosphate and nitrate due to rapid assimilation and regular removal of detritus.
However, in a tank with measurable phosphate and nitrate, these substances are available in higher concentrations on a
continuous basis.
In the natural reef environment, both scenarios can occur. As just two examples:
1. A large school of Surgeonfish passing over a particular area in the reef can supply a large burst of nutrition via their feces.
2. A deep water upwelling event can supply relatively long term nutrient enrichment.
Looking at this question strictly from the coral's needs, this begs the question: "Is there any advantage to having nutrients supplied intermittently while maintaining nutrient deficient water or is it advantageous to have them constantly available in more concentrated amounts?" In some studies, elevated nutrient levels have resulted in faster coral growth. In others, the result has been increased disease and bleaching (but I don't know the levels of elevated nutrients that the corals were subjected to).
My take-away from all this is that corals can do well in the aquarium using different strategies and techniques as long as their energy needs are fulfilled.
Ralph.
