What do nitrifying bacteria really want?

Yes, that's all it is!

Are they suggesting that at higher levels of ammonia (X? ppm) there is effectively TOO MUCH food for our ammonia eaters and the population's growth is inhibited x%?

Yes. We noticed that ourselves when people tried to "speed up" fishless cycling and gave a dose >5ppm.

If so, what is the correct dosing level for quickest fishless cycle?

We've been noticing that `5ppm is the max. But perhaps the "max" is not the fastest and most effective here... Personally, I feel that, as long as there's a detectable amount of any food, the bacteria that use that resource are still multiplying as fast as ever they can. A general fact of bacterial life. Once they're using up all of maybe 2ppm ammonia, you can sneak them a little more.

How much is too much? We don't really have the "Xppm"-- and they don't really, either, I guess.

Is there any other Tom-level conclusions I should draw here?

Perhaps there's less than meets the eye, eh.
 
Actually, it means that the high ammonia concentrations inhibit the bacteria that break down the second stage--nitrites--rather than impacting the ammonia consuming bacteria. If I read that correctly.

Part of what I am curious about--is the inhibition of the bacteria's ability to process nitrites, or the ability of it to reproduce? I don't know how closely tied those two features are in bacteria, and my instinct is that anything that slows it's consumption slows reproduction similarly, though somewhat delayed? And, is it the ammonia, or is it the presumably decreased oxygen supply (thinking that an increased concentration of ammonia reduces the amount of oxygen dissolved in the water)...Which then factors in with pH, right?
 
DO and pH should be independent per se , but could in theory result in less than optimum DO due to biomass utilization (especially at 29C). But in the real world of tanks, O2 shortage should not happen. Note: I said should not , I did not say "does not"

In fact, it does not matter which bacertial type is suppressed, or whether the inhibtion is metabolic or reproductive - the end result is the same, interruped cycling. The two functions are awfully closely related in most bacteria anyway.

Remember, for these bacteria, nitrate is not primary food for mass-building, but primarily food as energy source - effectively what carbohydrates are to us - oxidizing either ammonia or nitrite yeild the energy with which the bug operates it metabolism. But for cycle purposes, we are more interested in building colony numbers (these bacteria are slow to multiply) which can then metabolize the quantities of metabolites which we need oxidized.

Edit: dissolved gases, including ammonia and O2, should be independent. One does not surplant the other.
 
Okay--that makes sense. So (and I show my lack of chemistry here), the oxygen levels remain constant as ammonia increases, but does the ammonia also inhibit the ammonia consuming bacteria (literally starving in the land o' plenty), or just the nitrite consumers? Would it make sense to try building the population of nitrite consumers before the ammonia eaters?

I understand that the amount of oxygen remains constant for a given sample, but if there is more ammonia, could it be that the additional ammonia spreads the oxygen thinner? The bacteria would encounter 4 ammonias for each oxygen (for example!), and can't process the first ammonia until it encounters the oxygen molecule. Wouldn't this slow it down? Since it sounds like these samples were not agitated, the bacteria have to wait around until the natural slow movement of the solution brings the oxygen around. In a tank, though, this should not be the case, since filters move the water--with both ammonia and oxygen across the media. Does that make sense?
 
Oooo! Ooooo! (hand shoots into air)

OG,

My guess would be that ammonia density would not alter the bacterium's odds of running across an O2 molecule since the premise is that the O2 saturation is the same in each case. I base this on a middling knowledge of statistics and probablities, not on any specific knowledge of chemistry.

How'd I do Teach?
 
If the sample size remains consistant, yes, but if you take a sample that already has a specific DO concentration and add ammonia to it, wouldn't that change the ratio?
 
well yeah but we are talking about fairly low densities of ammonia (ppm) so effectively the change is nil.

If the O2 density was 100/1,000,000 and you add 5 ppm ammonia now the density of O2 would be 100/1,000,005. Not much difference there, so Mr. Bacterium would have essentially the same odds of running across O2 in either soup.
 
Got it. I don't think in terms of numbers well--I prefer organizing my data to sit politely in rows and columns. Thanks!
 
Also, any nutrient can beome toxic at some level - I mean, it would be possible to drown in chololate syrup. Ammonia is remarkably soluble, so there have to be levels at which it is toxic to the ammonia users. We have the rather high figure from the research for optimum, you have to imagine that toxicity would be well past that.

I find it impresive that the optimum temp is at 29C. That is a level we can reach in our tanks without extra heating.
 
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