Originally Posted by
Amphiprion
Like in the thread on NR, we've known this stuff for a while, so I can't necessarily argue that. Some of FD's facts weren't quite right, like saying algae don't actually store P (they do) and, naturally, he wouldn't admit that, but by and large, that is what happens. We argued this back on RC years ago. What I think he has portrayed completely inaccurately is the actual rate in which this stuff happens on a typical time scale in our systems. I think he was very misleading, before conceding a bit, that this takes a good long while to happen and it isn't just 5-10 years, either. I think in reasonably healthy systems that this can take a good long time, more like 15-20 years, barring other disasters. He was also inaccurate about live rock, somehow thinking that it was able to purge itself when it ends up doing the exact same thing (considering many people end up "cooking" older live rock to prevent this). Even in his more ideal system with no sand and just live rock, large skimmer, and water changes, the rock will eventually be an issue--I've had that happen before, too. He'd still have to tear down the rocks the redo things eventually, possibly even more often than someone with a long-term sink for it. That being said, which would you rather do? Have a relatively trouble free tank for a long time, allowing nature to do its job or one that requires maintenance constantly? I've been down the latter path and I will never do it again, considering that missed maintenance one time could be absolutely crucial. As I said before, it is one of the most expensive, labor-intensive ways to go about doing this. We know that scrubbers can still grow corals (despite what was being said)--exactly how much "extra" growth is there to be gained from reef levels of phosphate? I'm not convinced it is terribly more significant and the tradeoffs, in my experience, are worse (i.e. starvation). If it really is that much more significant, I'd have to see it quantified to really lean in that direction. Of course, it would have to be appropriately quantified in an aquarium to begin making comparisons, since we'd need a baseline in our tanks to even start comparing to natural reefs. I think all of this would've fallen on deaf ears in the other thread, though.
In that same vein, there was a study I read a few months back that showed an increase in growth (at a reduced skeletal density, which decreases inversely with P concentration) with ever so slightly elevated P and that lack of growth is not a reasonable nor accurate sign of eutrophication/enrichment. If I can find it, that may be one blow against a portion of this argument. Not that I think that high P is good by any means, but that keeping it at extremely low seawater levels may not be completely necessary. That being said, I don't think FD's tank is as free of phosphate as he'd like to believe or have anyone else believe, either, all things considered.
Beyond that, I think there is more going on than meets the eye here and that it is being oversimplified, not accounting for other mechanisms (Occam's razor, I know, but probably not an unreasonable line of thought). I may have to consult some classmates and professors who are actually Ph.Ds in marine sciences in the hope that they may know more or have more insight. None, unfortunately, are chemical oceanographers, so I'm not sure how much they would be able to help in our exact situation. Shouldn't hurt to ask, though.