This is an excellent debate hitting a lot of good points. Lets be frank, while the nitrogen cycle is discussed as a series of sacrosanct points it would seem some, if not many of the details are based on theory rather than experiment.
Some points to argue - nitrogen fixing - wooden reeefer, you contradict yourself a little in your last post when you acknowledge the role of 'fixing' nitrogen by cyano. , and thne wonder if N2 fixing bacteria are present in significant numbers - I tihnk most of us would acknowledge (usually sadly) that cyano is present in large amounts, but is hopefully managed except in unfortunate circumstances.
Advection - maybe forced injection is too strong a term, but it seems to have been demonstrated that advection is a method of moving water thro' sandbeds. I could not say whether it is more important than diffusion, but they're both there.
trpeek hits an interesting point when he notes that with a layer of aerobic on top of anaerobic bacteria, the nitrate is generater in the aerobic layer, and 'passed onto' the anaerobic. I have no argument with that, however what is the situation for nitrate hanging around in the water column. Does that go thro' the layer of aerobic bacteria, or is it bounced? I don't know.
I have questions about the relative vigour of the reactions that oxidise ammonia and reduce nitrogen. It seems to me that in a strongly aerobic enviroment (our tanks) it is much easier for a bacerial enzyme to oxidise something than for another to reduce, fighting the oxidative enviroment as well. Thus you would need a far greater population of reducing bacteria, as they work more slowly I presume. Is that correct? If so, that can explain a lot about sand bed seeming more effective than surfaces (live rock, or even worse, bioballs) at dealing with nitrate - more area for populations of reducers.
'i have a verry difficult time believing that no bactiera was found inside the LR. have you ever cracked open LR?<many times, and hundreds of other rocks too> if there is no bacteria in there where is the sulfur smell and black areas coming from?<you can see this in all sorts of rocks. In this case the bacteria might have been there at burial, and be long dead... The main deal is the question re communication with the ouside world.>
also cooking LR devoids most if not all photosynthetic life from the LR. if there was no bacteria, the cooked LR's denitrifying abilities would be severly hindered...yet it isnt...<surface bacteria?>
One thing I've noted is that some people with big algae battles are never able to get back to a good situation, despite skimming, phosphate removers and so on - maybe the algae has outcompeted their bacteria to such an extent that the bacteria are almost all dead with only relic populations, if anything, left.
