Galleon, thank you for posting this article! Locally what I am happy see occasionally posted when newbies ask question about "ideal" water conditions beside being given "numbers" there are also admonishments not to chase numbers. As Sprung said a long time ago in his monthly column there is much we can only determine "Qualitatively not quantitatively". Regarding ULNS aquaria Charles Delbeek said in
Coral Nov/Dec 2010 pg 127 "Our crystal-clear aquaria do not come close to the nutrient loads that swirl around natural reefs. And so when we create low-nutrient water conditions, we still have to deal with the rest of a much more complex puzzle." I do not see the artice linked in the first post as advocating high phosphates but pointing out that phosphates are just part of the equation. It is not enough to just know that phosphates are usually low in wild reef systems but we need to know exactly why and what that means in our captive systems. We also need to know why phosphates are linked to algae problems in some situations but not in others. I personally am very interested as I see systems that are struggling because the aquarist is blindly chasing a zero tolerance towards ammonium, nitrates and phosphates when these nutrients are critical for corals(1)(2)(3). Beside the role corals along with their symbionts take in arguably being the central part of the filtration in our systems what also does not seem to be recognized by very many of the experienced aquarists and self appointed "Gurus" is just like people corals can not only be anorexic, starved with little brown coloration from Symbodinium spp. dinoflagellates, but also obese, or have too many symbionts.(4)
(An item that I did not see mentioned in this article is phosphates are a limiting nutrient for hermetic corals uptake of nitrates(2) which raises the question of nitrate issues being caused by not enough phosphates.)
For the record I do not advocate high phosphate levels and I do not want the following observations/post to be misconstrued as such! The following tank has been maintained for over 6 years with tap water. Initial phosphate test with Merk/Tunze High Phosphate was less than .25 ppm PO43 (no discernable color change, lowest color reference was .25). Within the last month the phosphates in the tap water tested as .14 ppm PO43 (Elos Professional). No GFO has been used in this system since the original acrylic tank was replaced with a glass tank in March of 2011. Water changes are every 10 to 21 days, mostly 10 - 11 days and on average a cup of Xenia is removed each month. In May 2011 the phosphates tested as 3.0 ppm PO43 (Merk/Tunze high phosphate) (Yes, that's 3.0 not .3). Two months ago the phosphates tested ~1.0 ppm PO43 (API, off the scale with Elos Professional), nitrates were undetectable with API. Two items of note, when I started maintaining this system 6 years ago there was both a serious Aiptasia and Valonia algae problem which have significantly abated with minimal intervention on my part. Herbavores are Cherub and Coral Beauty Angels, A yellow and two regal Tangs and a handful of hermits. Clearly SPS, or at least Green Slimmer, Bink Birdsnest and Montipora digitatus can be maintained with high phosphates without algae problems. AND! More importantly, reef aquaria can have processes that reduce the phosphates without external intervention.
http://www.youtube.com/watch?v=9Eckf4Jne40 May '11 PO43 ~3.0 ppm
http://www.youtube.com/watch?v=-eCQSVdqBQA Sept. '13 PO43 ~1.00 ppm
And considering calcium carbonate will dissolve in reef aquaria with the help of biological processes I am dubious of the claim it is being absorbed by the rock. This photo is of part of the Birdsnest colony from the above sysem that was killed when the colony was pruned. It shows the surface detail from part of the skeleton that was freshly dead (right side) and was not exposed to saltwater and part that that died from lack of light and was in the tank exposed for less than 8 or 9 months(left side). (Pruning was required because the colony had reaching the surface and would have started tabling killing off everything beneath it):
(1)
http://www.ingentaconnect.com/content/umrsmas/bullmar/1979/00000029/00000004/art00011
(2)
http://jeb.biologists.org/content/214/16/2749.full
(3)
http://wap.aslo.org/lo/toc/vol_48/issue_6/2266.pdf
(4)
http://www.sciencedaily.com/releases/2012/10/121014162914.htm