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RE: [Killietalk] Cloromine (sic)
Thanks Wright, I had it backwards. Those figures help alleviate my
concern for the effect of pH changes when I change water. There I'm
usually going from 5.5 (or on REALLY bad days 3.5) back to 7 and used
to be concerned that ammonium (at the low pH) would disassociate to
ammonia and H+ and cause problems. Your chart show that this doesn't
happen till we get way up around pH 9. I knew it happened but wasn't
sure where along the pH scale.
-----Original Message-----
From: Wright Huntley [mailto:whuntley at verizon_net]
Sent: Monday, February 02, 2004 3:14 PM
To: killifish discussion list
Subject: Re: [Killietalk] Cloromine (sic)
It's the other way around, Edd. St. Louis is almost a worst case
scenario! All the more reason to be startled at Charles's success.
There's an equilibrium ratio of harmless ammonium ion (NH4+) and toxic
Ammonia (NH3) that depends on pH (and temp.). High pH converts more to
the deadly form and pH below about 7 produces so little we usually can
ignore it.
Some typical percentages are (at 20C):
pH NH4+ NH3
7.0 99.5 0.5
8.0 95.3 4.7
9.0 64.2 35.8
9.5 38.9 62.1
At 15C that last number drops to 57.6, but would also increase a bit at
higher temps. The 50% crossover point is between 9.0 and 9.5. Below that
pH, more is harmless ammonium ions. Above that, more is as deadly
un-ionized ammonia.
Increasing dissolved oxygen also greatly reduces ammonia toxicity.
Don't forget that we see so much ammonium, and so little ammonia, under
normal circumstances, that we tend to forget that ammonia is potentially
harmful at way down around a few parts per billion. Even the 1.5% at a
pH of 7.5 and a temp. of 20C is quite significant, based on the studies
cited in Spotte (_Fish and Invertebrate Culture_), if total
ammonium/ammonia is around 1 ppm ( a common value). They calculated
levels of 6-8 ppb caused significant gill damage and permanent stunting
in baby salmonids. YMMV and Charles's obviously does. :-)
Folks have said they have been getting away with it. Well, I,
personally, did not, which may explain my tendency to go on too much
about it.
We had a unfortunate backup of San Jose water into our Santa Clara well
pipes. When I saw the fish in distress during water change, I started
testing and detected chlorine. I immediately popped in some dechlor
product and promptly killed some of my fish. Apparently the low-level
chloramine (which was totally unexpected) did the fish less harm than
the subsequent release of ammonium/ammonia. My normal pH was high and
the water quite hard (8 and 450 ppm). IDK if the San Jose water was
similar, because I was too horrified to think and measure it. I have a
hunch it was RO water that had added CaOH to raise the pH, as well as
the chloramine. I only found out it was chloramine, later. All this was
years ago and should be measured against my memory (which is still my
second-shortest thing).
When you lose a few favorite fish, and are quite sure it was because the
hypo acting on chloramine killed them, you can be made a believer very
quickly.
Wright
Kray, Edd wrote:
> One question on this chloramines controversy. How does the rather
> aberrant pH of St Louis water effect this situation ? I recall that
the
> pH there is close to 9. Doesn't this effectively reduce the toxity of
> the ammonia released by the hypo. Whereas in a situation with more
> normal pH (7), the ammonia might be a real problem. So experience
unique
> to St Louis may not apply to the majority of the rest of the US.
>
--
Wright Huntley -- 760 872-3995 -- Rt. 001 Box K36, Bishop CA 93514
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