[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: pH VS ammonia
Hello,
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.
Best,
George
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
> experienced.
>
> 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
> diseases.
>
> 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
> recovery.
>
> 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
> situations.
>
> 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
>
> --
> Wright Huntley, Fremont CA, USA, 510 494-8679 wright at killi dot net
>
> http://www.atchison.com/Killifish/BAKA-WCW-10.html
>
> For all you ever wanted to know about West Coast Weekend X
> The great killifish show and convention, combined with West Coast Live
> ---------------
> See http://www.aka.org/AKA/subkillietalk.html to unsubscribe
---------------
See http://www.aka.org/AKA/subkillietalk.html to unsubscribe
Follow-Ups:
References: