Well what makes me curious is that just a Day after Changing the water the
PH raises....
I m still looking for factors that might effect the buffering issue..... I
came over the hardness issue due to the RO system and this is one good
thing.
The only problem is tying to maintain a PH value of 6.8-7.0 (I m
optimistic.....)
I do have 4 tanks which in all I have about the same GH and almost the same
PH (7.2-7.4)
In my planted one I use a CO2 system and its fully planted with not many
fish.....
Maybe I 'm missing something about the buffering but are there other
parameters I might look for ?
10x again

gizmo
"Racf" wrote in message
hlink.net...

"gizmo" wrote in message
...
Well after learning a bit more about RO systems....
When I do change water in my tanks I use 75% RO water to get a PH rate
of
about 6.8 and GH of 6-7.
But after a while (about a week) the PH value is going up a bit....
What are the factors of a PH raise it raises up to 7.2 (The hardness
stays
the same ,though these too parameters as I understand are not
influenced by
one another) ???
10x

gizmo




Here is an older post that provides information about pH and kH data,
and a bit of other information that may be interesting:

From: Nestor10 )
Subject: What are optimal soft water characteristics?
Newsgroups: alt.aquaria, rec.aquaria.freshwater.cichlids,
rec.aquaria.freshwater.misc, sci.aquaria
Date: 1998/05/29


The most important equation is the fish you want to keep and their
preference.

I, as do many others, usually recommend trying to keep fish that are
compatible with your prevailing water conditions. This makes for much
easier
fishkeeping all around, and has been reasonably explained many times in
these groups - I don't think too many people want to hear me go through
it
again. This case is a little different, though, as Kelly has already
decided
upon the types of fish she wants and has also taken the initial step of
softening her tap water.

KH refers to the carbonate level of the water with an aquarium having
50
ppm being on the acidic side. Very low KH will lead to swings in the pH
due
to the low buffering capacity of the water. A high KH 200 will tend to
give
an alkaline condition.

This is mostly true, with only a slight error. KH measures alkalinity as
an
equivalent amount of carbonate hardness. Carbonates and bicarbonates are
normally the most prevalent types of buffers found in aquaria, and their
effect tends toward the alkaline side of the pH scale. A buffer,
though,
does not have to be alkaline in nature - there are acidic buffers as
well.
Buffers do their work by absorbing changes to the system, thereby
"buffering" the system from the addition of either an acid or an alkali.
Having a low buffering capacity does not accurately imply an acidic pH,
but
does point out that the system cannot absorb much of an acid or an
alkali
and still remain stable.

KH test kits are most often based on acid titrations. This means that
you
begin with a test sample and slowly add an acid of a known specific
concentration until the pH changes in proportion to each new addition of
the
acid. The buffer will "absorb" the increase in hydrogen ion
concentration as
long as there is buffer available to do so, and after that the free,
unabsorbed hydrogen ions cause that ionic concentration to increase and
along with it a measurable decrease in pH. The color change you see in
the
test itself is merely an acidic indicator - once the alkaline buffer is
exhausted and there is a corresponding increase in hydrogen ions, the
now
acidic solution causes the color to appear. Since the color change only
indicates a increase in acidity, there is no need to try to determine
the
shade or intensity of the color. Hence, no "color chart" for comparison,
as
with so many of the other types of test kits.

By counting the drops of acid until the buffer is used up and the color
change indicates an increase in acidity, we know how many hydrogen ions
have
been added (and absorbed) in order to use up the buffer in the sample.
Knowing the amount of hydrogen ions added and knowing how much carbonate
it
takes to abosrb those ions is simply a straight-up conversion factor.
That's
the biggest reason KH is measured in equivalent amounts of carbonates,
and
the reason it is most often referred to as "alkalinity". If we were
testing
for the capacity of an acidic buffer, like the phosphates, then the
situation would be reversed - an alkali would be added until the
indicator
marked an increase in pH (meaning a sharp decrease in the hydrogen ion
concentration or an increase in the hydroxide ion concentration). Then
we
would probably be calling it a test for "acidity".

GH is a measure of calcium and magnesium dissolved in the water. Hard
water is generally 150 ppm. If GH is 50 ppm, pH levels can have
swings.

GH, or General Hardness, is a measure of the earth alkali compounds
present,
and only considers the cation, or positively-charged portion, of the
molecule. It does not take into account the buffering capacity of the
water,
so its level, either high or low, has no direct bearing on pH
measurements.
The two most prevalent types are, indeed, calcium and magnesium, but
those
elements form combinations that may or may not affect buffering. Thus,
250
ppm of calcium chloride would make the water every bit as hard as 250
ppm of
calcium carbonate, but would add no buffering to the water at all.
Conversely, 250 ppm of sodium carbonate would mean highly-buffered
water,
but its sodium cation wouldn't register on a GH test. Sodium chloride
would
affect the TDS (Total Dissolved Solids) without touching either GH or
KH.

The reasons and mechanics of pH swings in a lightly-buffered tank have
been
the topics of many discussions. It is a pretty straight-forward process,
making even more sense once buffering is understood. Because of the
frequency of the topic, and the fact that I've already rehashed
GH/KH/TDS, I
won't "lecture" on that. If you have questions about it, though, and
can't
quite find the answers in the FAQs or DejaNews archives, then by all
means
ask.

Going back to Kelly's situation,

What are the best settings? I'm thinking of PH being around 6.5-6.7.
I'm
particularly afraid of PH fluctuations (bounce). What other parameters
am I
missing?

The answer to this - especially the "missing parameters" part - has to
be
given with consideration to her previous posting of the same general
natu

I have an Aquarium Pharm water DI unit that I use to purify tap
water...when I add Sodium Bicarbonate...this sends PH through the
roof...

Sodium bicarbonate is a widely-recognized method of increasing the
buffering
in order to stabilize pH. (By the way, you're looking for a minimum
target
of 4 - 5 KH, or 80 - 100 ppm, in order to stabilize the pH.) I would
caution
against the bicarb in this case because of the sodium. It is my
understanding that the API resin softener is one of the units that uses
the
lesser expensive sodium zeolite in order to "soften" the water. It
exchanges
two sodium ions for each calcium or magnesium ion pulled from the water.
Most black water types of fish come from acidic, low-pH waters that are
also
very soft. That includes not only GH and KH, but TDS (especially in the
form
of salts such as those of sodium) as well. So, while the "purified"
water
may not register on a test for hardness, there would still be minerals
present in the form of sodium salts. Adding sodium bicarbonate would
only
compound the problem.

I would suggest increasing the buffering through the use of a
slow-to-dissolve form of calcium carbonate. Some hard limestone
decorations,
partial mixing of the substrate with a calcareous sand/gravel (crushed
coral, limestone, etc) or placing a few sea shells or oyster shell in
either
the tank or the filter might be the way to go. Even better, since you're
also concerned about trace elements, you could try mixing your filtered
water with some unfiltered tapwater to reach the desired hardness.
Determining the mixing ratios is fairly easy - cutting hardness of any
type
is directly proportional. An example would be cutting the hardness by
75% -
one part water at 100 ppm mixed with three parts purified water
(presuming 0
ppp) yields water of 25 ppm.

-Y-

http://www.mindspring.com/~nestor10

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