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- May 22, 2016
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The narrative seems to be that dosing organic carbon shifts the microbiome to being more heterotrophic and less chemoautotrophic. This in turn renders two risks. One is altered coral associated bacteria (coral can become sick) and the other is a diminished chemoautotrophic bacteria population (the risk is having nitrification shift from a system that works by itself versus one that is actively managed by carbon dosing, i.e., passive control is inherently safer than active control).
From what I have read from Rohwer and others, when excess DOC is rapidly delivered to the coral the current prevailing theory is that the coral's own resident bacterial population overpopulate and this starves the coral of oxygen.
To me it's a bit ironic that the studies on some DOC having detrimental effects on coral are used to target Carbon Dosing as a bad idea, when algae is the actual study design emphasis.
The studies are meant to explain why algae-derived DOC are harmful to coral. I.e. how algae in close contact causes coral health decline. The research is pretty clear, the DOC from the algae affects the O2 levels but more importantly the microbiome of the corals (antibiotics can save corals from detrimental effects of growing too close to algae).
But those studies use either algae itself, or DOC sources that approximate algal sources.
These studies aren't using acetate or ethanol.
Maybe @Belgian Anthias could point to studies on detrimental effect of acetate addition on coral microbiome?
If you were going to use a big algae scrubber, these papers could be a reason to think hard about it (though it seems to work for many).
If you were going to pour glucose or galactose or mannose in your tank, these papers would be a reason to reconsider.
If your carbon dosing routine is 2 teaspoons of sugar in your coffee and one in your tank, then yeah....don't.
But these papers don't show that acetate (or ethanol) has these effects, it doesn't take much experimenting to realize different carbon sources are used wildly differently in a tank by organisms. (Try it! bottle up tank samples and add equal C of different DOC sources - differences are naked-eye apparent. It's wild.)
So simply stating that carbon dosing, as practiced in the hobby, has been proven detrimental by these studies is incorrect. It could be, but that requires assuming acetate and ethanol act like glucose, mannose etc, when my eyeballs tell me they don't.
By the way, if I use the elevated C/N ratio of input fish flake to keep NO3 low, the excess carbon input is stuff like "wheat gluten, wheat flour, wheat starch..." not sure those are better Carbons than acetate either.