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Recent threads, mostly on CO2 (do we even have any others?) have shown some
attitudes toward pH that are, IMHO, quite unwarranted. I intend to make a
few blanket statements, based on my experience, that I'm prepared to defend.
Unfortunately, many books and LFS clerks have wildly *different* opinions,
so it behooves us to seek the truth, wherever we can find it. That said,
1) Fish are remarkably insensitive to pH alone between about 4 and 10, and
they don't react to it unless some secondary factor is present, that
altering the pH changes -- like converting ammonium to ammonia. [pH below 3
can maybe kill some fish. I accidentally did it to some baby Cories, once.
2) Plants may have slightly higher sensitivity to pH, tds, hardness, etc.,
but the boundaries are probably wider than we usually hear about here.
3) There simply is no such thing as "pH shock." The fish can't feel or taste
it, and I routinely subject delicate fish to abrupt changes of 2 or more
points. In the Scheel _Atlas of Killifishes of The Old World_ he claims
sudden swings of over 3 points have no effect. An unfortunate connection
between alkalinity, tds (osmotic pressure) and pH started the myths, and
many authors have ignorantly propagated them to this day.
[Don't subject your fish to sudden large changes in dissolved solids (tds)
for that *can* kill them for sure. They need time to adjust their osmotic
4 ) pH is a useful thing to measure, along with alkalinity (unfortunately
confused with hardness by calling it "carbonate hardness") primarily to use
the CO2 concentration equations or charts to set the CO2 level for proper
[Trying to otherwise adjust the pH chemically, to some false ideal, just
creates a chemical soup and *more* stress on the fish, and even more lush
algae, under most circumstances.]
Keeping the pH from going low in the presence of nitrites and heavy metals,
or high if a lot of ammonia is present, is a prudent thing to do to keep
from simply poisoning your fish with these pH-related toxins. Good
water-change practices and heavy planting virtually eliminates these things
[I learned the hard way to keep lead plant anchors out of low-pH, salty
Neither fish nor plants really like tds shock, for the cells have to adjust
to maintain proper concentrations of various salts in the internal fluids. I
am observing that I kill less "wanted" organisms by paying attention to tds
change, than I ever did when I thought pH was some kind of magical thing.
YMMV, but I'll still put up the old flame shield, just out of habit. (^_^)
Wright Huntley, Fremont CA, USA, 510 494-8679 huntleyone at home dot com
"People constantly speak of 'the government' doing this or that, as they
might speak of God doing it. But the government is really nothing but a
group of men, and usually they are very inferior men." --H. L. Mencken
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