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Re: pH VS ammonia
I just have to jump into this discussion. This is a good example of
chemical equilibrium at work:
As the unionized ammonia (NH3) is removed -- by ANY action -- the
equilibrium will shift and more unionized NH3 will be produced, to keep
the ratio ammonium:ammonia (NH4+:NH3) constant.
So, as the NH3 is being continually removed, all ammonium will be
converted to ammonia -- and removed!
One thing of practical importance that we don't know is how FAST the
ammonia will be removed, thus how fast the water will be detoxified.
Wright Huntley wrote:
> Charles n Sue Harrison wrote:
> > As long as the pH of the water is below 8.5 the effect of ammonia in
> > not a problem. as a matter of fact, the ammonia if present would
> > remain as its salt even if the water were boiled away to almost
> > dryness.
> It is tough to argue such points with a chemist, but I must respectfully
> disagree, both from what I know through reading and have directly
> Yes, the ratio of ammonium to ammonia is theoretically constant at all
> concentrations if it is evaporated away without heat. It varies most
> strongly with pH and to a lesser extent with temperature. In your specific
> example, the ammonia will quickly boil off as gas, and leave *only* the
> harmless ammonium ions. That's not what happens in an aquarium, though.
> There, the tendency is for the fish to produce more all the time.
> Ammonium and ammonia have an equilibrium relationship that varies with pH
> and temperature. The percentage in the dissolved but not ionized ammonia
> (NH3) form, at 20C, jumps from 0.5% at pH=7 to 13.7% at pH=8.5. [Spotte,
> 1970, p104] That means that 86.3% remained as the ion (NH4+) form, so you
> are correct, in that *most* is still harmless ammonium.
> However, the basic *toxic* material is over 27 times higher at a pH of 8.5,
> until we do something to remove it, such as long-term aeration,
> biofiltering, plant feeding, etc. In any compromise between food and poison,
> the poison will inevitably win.
> The overall toxicity of ammonia can be altered by lots of other factors.
> Supersaturation with oxygen seems to reduce damage, somewhat. Nevertheless,
> ammonia is lethal at levels well below what the average test kit can
> indicate, and the stunting and subtle disease-inducing damage can be severe
> at far, far lower levels.
> Spotte goes on to point out that Burrows (1964) found clubbing (hyperplasia)
> and permanent damage to gill filaments of salmon fingerlings at levels of
> ammonia of 0.006-0.008 ppm (0.3 ppm total ammonium/ammonia). [This was at a
> pH of only 7.8, BTW.] The younger fish never recovered, when returned to
> clean water. They were stunted, permanently. Older fish did recover after 3
> weeks in new water. Results on minnows and other fish were much the same, so
> the damage was deemed to not be species specific. Burrows suggested that
> exposure to ammonia at such levels also was the precursor of bacterial gill
> Betta owners often do frequent, 100% water changes. In recent years,
> literally thousands of Bettas have been killed when the dechlors based on
> thiosulfate were used but the city water had changed to chloramine. It was
> more obvious with them, because the ammonia was so much higher level with
> 100% water changes. It was quite lethal in water of pH only in the mid 7s.
> It made real believers out of a lot of Betta folks, particularly when that
> year's co-Grand Champions were *both* completely wiped out, by ammonia, at
> opposite ends of the country!
> In killies, I have seen numerous examples of sickly fish and sudden breeding
> failure due to the same problem. Incredibly tiny amounts of ammonia can
> sterilize wild rainforest killies almost completely. If exposure is low
> enough, they sometimes recover fertility. We nearly lost one of the
> still-unidentified TDK 97 Gabon species through this (or a related)
> mechanism. Luckily, they started producing viable eggs again after months of
> While Spotte and Burrows seem to think the effects of ammonia are not
> species-specific, like some organic metabolites, I have a feeling that some
> of the harder-water species are a bit more rugged and tolerant than fish
> that really need soft acid water, wild fish, or fish with very high
> metabolic rates. Maybe the damage is comparable, but they just show the
> results differently.
> Anyway, Charles, until you have been there and experienced it for yourself,
> I suggest that advising folks that ammonia isn't a problem at pH=8.5 is not
> a really good idea. You don't have the same fish or local circumstances that
> they do, and the overwhelming evidence is that control of ammonia is the
> single most important water factor in most artificial maintenance
> You can add ammonia-containing fertilizers if you like. I have killed wild
> Amazonian fish by stupidly using a fertilizer that I didn't realize
> contained ammonium nitrate, in a planted tank, and it was in really tiny
> amounts, too.
> That's my $0.02 (again) on the subject.
> Wright Huntley, Fremont CA, USA, 510 494-8679 wright at killi dot net
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