Here is an excerpt of a post written on the pH "myth" by
daveedka on AquariaCentral.com. Dave is most excellent at explaining
stuff so that even a noob like me can understand :)Perhaps someone
can take this further and form a theory?
. . ."I do own Ph test kits, and do use them, but seldom worry about
what my PH actually is or how much different tank and tap Ph really
are. The fish react to the level of dissolved solids, not the actual
ph of the water. PH "shock" as it is commonly called in the hobby is
actually Osmotic shock caused by taking a fish from water with one
TDS (total dissolved solids) level, and putting them in water with a
far different level. This interferes with osmo-regulation and harms
the fish (or in mild cases stresses the fish) fish can and will
adjust to changes, but it takes some time. My tanks range from 6.6-
7.2 Ph with co2 injection, my solids levels and Carbonate levels are
constant and consistant with my change water. the fish don't know
the difference in the ph.
All of this is of course within the ranges of normal Ph's. Extreme
high's and lows will still do harm, but seldom does this discussion
ever contain the extremes. I have seen tanks with OTS that regularly
tested at ph of 5 and the fish survived. and likewise I have seen
fish kept in tanks with ph of 8.8 with no problems.
That being said, the Ph myth is huge and largely mis-understood.
It comes from the fact that what we as humans view as hard water is
far different than hard water in the sense that fish care about.
Human hard water is water that is hard to get soap suds in, for fish
it is water that is high in TDS (total dissolved solids). A person
can take RO water and adjust it to a Ph of 8.2 and have less
dissolved solids than high calcium water would have at a ph of 7.0.
The Ph correllation is extremely general and far too much emphasis
is put on it. Here in Columbus Ohio we have tap water that is
pathetically devoid of everything. Our water comes from the pipe at
close to 7.0 ph most of the year. it changes to 7.6-7.8 after
sitting out for a while. Now the crux of the matter is: there isn't
enough calcium, magnesium, trace minerals etc. in that water to grow
plants, snails, or shrimp. By all rights our tap water at 7.8 ph is
nearly perfect for ultra soft water fish like tetra's and discus.
Mollies and swordtails will not breed in our tap water because it is
so soft. on the flip side I can take that same water and make it
rock hord with calcium and magnesium and never alter the ph one
iota. Then I have water ideal for rift lake fish, mollies, snails,
shrimp etc. and the ph is still exactly 7.8.
A water softener exchanges calcium and magnesium ions for sodium
ions at close to a 2 to 1 ratio. In other words the water going in
is high GH, we double (general term not mathmatically accurate) the
dissolved solids, and it comes out reading a lower GH. Discus would
rather have the water before it was "softened"
Now thus far we have talked about calcium and magnesium, and of
course carbonate. Our GH test kit picks up an Ca and Mg, but does
not read other items in the water. Our Kh test kit picks up on
Carbonate, but does not read other factors. So we could feasably
have high iron, high sodium, high sulfur etc etc. And our test kits
read ultra soft water. Dump a discus in a high sodium high sulfer
tank sometime (please don't do that for real) and you'll find out ph
Kh and GH readings mean next to nothing in the total picture.
Likewise we could take ro water add enoguh calcium and magnesium, to
get a gh of 18-19 dGH and just enough carbonate to get a KH of 3dKH
and we would have a ph of 7.8 or 8.0, Medium hardness reading,
medium to low Kh and high Ph. With nothing else in the water, our
fish would still see it as very soft water.
There are so many variables in the PH discussion, and so many right
and wrong ways to influence Ph that in the end it proves to be a
somewhat useless number. It is good for viewing changes, it is
excellent for calculating co2 levels (if carbonate is the buffer and
not phosphate) but aside from that it is limited in what it will
actually tell us. Additionally because of the emphasis put on PH
readings by so many people in the hobby, it causes a lot of
confusion, a lot of headaches, and in many cases it kills a lot of
fish.
In the wild, the water works under different rules, we have large
volumes of water with small numbers of fish. A KH of 0 in the wild
is not a big issue because there is enough water to dillute the
effects of biological acidification a KH of 0 in our tanks is a
recipe for dissaster. Many People constantly work for a PH of 7.0,
when in fact they are setting themselves up for an unstable tank
environment when they do that. Our tap water at 2-3 dKH is Ph of 7.6
at atmospheric co2 levels. This tells me that unless I'm injecting
co2 I never ever want a tank with a PH below 7.6 PH.
When we use products like peat the tannic acid depletes the
carbonate, the calcium and the magnesium (at least that is my
understanding at this point) this is a good and useful thing to know
if we have extremely hard water and we want to raise Discus fish. It
is not a good thing if we don't understand the whole picture and we
over soften our water and crash the tank.
Trying to get the entire aquarium hobby to see this is difficult at
best."
Dunno if that helps you at all,
Eileen
(Roan Art)