What do nitrifying bacteria really want?

W

wetmanNY

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Every week or so, somebody posts here how their nitrogen cycle is stuck on "spin-dry" or something-- and I mumble something about nitrifiers being tender yada yada yada...

So here's grist for our mill:

G.A. Vazquez-Rodriguez and J.-L. Rols worked up a "Study of the nitrification process with activated sludge: inhibiting effect of ammonia on nitrifying bacteria" in Rev. Sci. Eau vol. 10 (3) : 359-375. ((1997) There's an English abstract .

The authors of the paper measured the respiration of nitrifying bacterial communities to assess the inhibition that ammonia exerted. The influences of pH, temperature, and the free ammonia concentration (NH3-N) were studied. The maximum activity of the nitrifying bacteria was found at pH 7.8 and at 29oC (ca84oF), with the 90% range of maximum activity lying between pH values of 7.5 and 8.1. For a concentration of 11.4 mg NH3-N, (pretty stiff) a nitrification inhibition degree of 60% was reached.

It's always handy to have some figures...
 
But what was the Color of the media they were propogating the bacteria on???

It's all about the color man...the pink and blue hues, flowing together...oh, got off topic there. Sorry!

90% btween 7.5 and 8.1 huh. Are the effects of ammonia on bacteria the same as fish? You know, the whole logrithmic (sp?) scale and ammonia being more toxic at lower ph? Ooh, almost had a cognitive thought:D
 
fishless cycling

So, people who are doing fishless cycling need to be careful if their pH is low? Even below 7.0? Is there some limit on the ammonia one ought to use when starting with low pH water?

I've always thought that the common method (?) of adding ammonia to keep the level at 5.0ppm daily seemed too much. More natural would be to determine ewhat ammount it took to get that high and then keep that daily addition lat that level (keeping the faux bioload constant)

anona, who cycled with a delicate fancy goldfish who now has curled gills
 
Did the article mention other concentrations of ammonia and their effect on nitrification? It would be interesting to know if the relationship is linear or non-linear...

Kinda sounds like 5 ppm isn't too high for fishless cycling.

Interesting bit of info, Wetman!

Jim
 
Yes they did. (Hit those html links, Schmidt!) In fact, they measured oxygen consumption ("respirometric measurements") at ammonia concentrations ranging from 0.1 to 70 mg NH3-N/l. That would include levels more like the ones we use in fishless cycling, RTR. Though the abstract doesn't give values for inhibition of nitrifying bacteria at other levels of NH3-N, the authors drew back from any sweeping conclusion: "Inhibitory effects of ammonia on nitrifying bacteria activity seem to be complex and strongly dependent on other environmental factors which modify the dynamics of biomass growth."


...hmm, maybe we coulda tol' them that!

Still, this kind of stuff relates pretty directly to our fishtank struggles, eh!
 
Thanks, Wetman. I hadn't noticed you had linked to the abstract -- I should have expected it, given your thoroughness. I might try to hunt down a translation of the full article or a citation of the article in English. It's been in print long enough that someone must have cited it.

Thanks again,
Jim
 
every group has one

and I guess in this case it is me. So I will ask the stupid question: what does this mean to me the fish keeper?

As I read it, fishless cycling happens quickest at a pH of 7.8 with a temp of 29*C. That much I think I understand. The inhibition thing confuses me though. 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%? If so, what is the correct dosing level for quickest fishless cycle? Is there any other Tom-level conclusions I should draw here?
 
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