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- May 22, 2016
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I agree with you - wading through the data about archaea is difficult - and unless someone who is an expert - that has read/synthesized all of the review articles on it, you will get conflicting results (just like you are with aquabiomics).
on the archaea,
aquabiomics has said that hobbywide most of the detected ammonia oxidizing organisms (or at least sequences) are from archaea. I think I'll dig up posted aquabiomics reports to see if that's generally the case, or if I'm misinterpreting this.
Now - one important caveat about what I said above - its only true if you're counting by species. Most of the nitrifying types are in the biofilm.
But in fact by far the most abundant ammonia-oxidizer in saltwater aquariums are not Bacteria, but rather Archaea. In this case they are free-living Archaea that live in the water column. So the often repeated statement that nitrifiers don't live in the water is not strictly true. In fact, in terms of cell numbers, thats probably where most of them are. But many types (especially nitrite-oxidizing bacteria) are much more abundant in the biofilm.
If hobbywide, everybody has sand that nitrifies somewhat, but nobody has water that nitrifies much at all....
1) the idea that the archaea are mostly doing their work in the water is wrong, and their activity is surface associated for us in the reef hobby.
or 2) archaea are much better at putting a bunch of genes in the water than they are at oxidizing ammonia in the water
or 3) aquabiomics protocol samples water well and biofilm poorly, skewing the results and making water-borne microbes look much more numerous than surface ones.
or 4) the premise is wrong, and lots of systems in the hobby have significant nitrification in the water alone, just not mine or @Dan_P (anybody ever actually observe this?)
@Brew12 has read a ton more cycling posts than most.
I wonder if he's seen any hobbyists find significant nitrification from tank water alone - no substrate?