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[APD] pH. Some facts and some mythology. [Starting a deviantthread...]
The typical LFS approach to tank chemistry seems to have left us with a
lot of folks here who get very, very exercised over a pH swing of a few
Fish and plants don't much care about pH, depite the popular mythology.
[OTOH, I have some magical herbs that will increase your sexual
performance, remarkably, if you do believe those pH myths! ;-)]
pH kits are extremely high markup items at the LFS, and most books have
been terribly inexact (even quite wrong) about the effects (or meaning)
of pH. It is easy to see that dramatic color change and even beginners
get a measurement accurate to a few tenths of a point. The real question
is, "What does that reading really mean to my fish and plants?"
My conclusion? Not very much. :-)
I have been observing aquarium fish, up close and personal, for about a
half century and was curious for at least a decade before that. I don't
think fish can feel, smell or taste a pH change! Can you tell the pH of
the water when you jump into a swimming pool? Is the burning in your
eyes any different from too much chlorine or from too-high alkalinity?
From my own observations, I suspect that fish can't really tell, either.
I'm quite sure that there is no such thing as pH "shock." Water changes
can cause *other* parameters to change, some of which kill fish, but the
pH is a non-involved one, or only an indirect one.
Sudden shift to higher pH can turn the equilibrium from harmless
ammonium to deadly ammonia, if any is present. The killer is the
ammonia. The excess of OH- ions just allows the ammonia to form. pH does
tell us the excess OH- ions are there, but doesn't hurt the fish of its
own properties. Neither do the OH- ions. [I know. Same thing!] Without
any original ammonium, the fish tolerate the pH-change quite easily.
Just-received fish are often victims of this effect, as the ammonium
they released in shipping is converted to a deadly burst of ammonia by
the new, higher-pH store water.
I would guess that the vast bulk of "pH Shock" cases are osmotic shock,
in which the fish are subjected to sudden drastic tds changes before
their osmotic regulators can adjust. That can cause wicked cell damage,
leading to illness or death. Soft and hard water often have very
different pH. If that's the only thing you know how to measure, it's
easy to blame the shock on the pH change and miss the real cause, entirely.
Measuring pH is not a useless exercise, but the results need meaningful
interpretation before they are worth anything.
How many times have we seen someone dope a tank into a chemical soup
with pH adjusters, Almond Tea, etc., and then complain that the pH-KH
chart doesn't give them the right CO2 reading? The chart, and measuring
the pH and KH, are quite useful, but *only* if the primary buffer is
carbonate/bicarbonate. If you add a bunch of other stuff and dose with
"Blackwater Extract" and other such snake-oils, or put peat in your
filter, don't use pH and KH to try to measure your CO2 levels. OK? Weak
humic acids from peat can work on pH just like the weak carbonic acid of
CO2 dissolved in water. Don't confuse them.
Super-acid pH can, in some species, probably cause blood alkalosis and
sickness. This is why folks with very soft water learn to fear the "pH
Crash" that happens as food decay products build up in tanks with
nothing to buffer them to the alkaline side. I suspect the decay
products are toxic and even more damaging than the low pH alone. This
gave rise to a myth that nitrites are deadly at lower pH. Phooey! It has
little or nothing to do with pH. It has more to do with sloppy
I have bred fish in tanks at around pH=4, and have never seen any fish
experience distress in a *clean* tank at pH even lower than that. If you
have no outside factor that poisons the fish, my general experience is
that most fish will tolerate any pH between 3.5 or 4 and over 10. I have
never hurt any fish by water change that suddenly changed the overall pH
by a factor of up to 3 points (for example, 6 to 9)* if no toxins are
present and osmotic conditions are matched. The fish are completely
Ammonium (at well below detection levels of the LFS tests, BTW) will
kill the fish as the ammonia is increased by over 50 times in the above
example. The trick is to be sure the original ammonium is *absent* (or
chemically neutralized). [That's why it is great advice to beginners to
just keep the pH at or just above 7.]
At the advanced level most folks keep tanks on this digest, that advice
is pretty primitive. Yes, you can shock your fish with temperature
change. You can really mess them up by suddenly switching them from
high-tds hard to low-tds soft water. Plant cells can be similarly
abused. Just because you learned to use a pH test kit, don't blame every
bad happening on the pH or its change. IME, it rarely is the real cause,
and is usually totally uninvolved.
I have a nice pH "pen" and some tds meters. I bet I use the latter 50
times more often than I use the pH meter. I'm learning what is
important, and what is not. My order of importance in most aquatic
endeavors is (Relative)Temp., tds, GH (and its relation to tds), KH and
GH vs tds is important because monovalent ions like potassium and sodium
are often lethal if not balanced by enough divalent ones like calcium
and magnesium for good cell metabolism. [This gives rise to myths about
plants or fish not being salt tolerant, even estuarine plants like Java
moss and Java fern. :-)]
*That is a change of concentration of H+ (or OH-) ions of a thousand to
one! As Tom says, that's a common daily occurence in some natural fish
Wright Huntley -- 760 872-3995 -- Rt. 001 Box K36, Bishop CA 93514
Education is what you must acquire without any interference from your
schooling. -- Mark Twain
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