Re: coral, pH, chemistry

[Doug Brown <debrown@kodak.com>]

>From Susan:

>I keep a small chunk of coral (about 2" long) in the basket of my
>AquaClear filter >and it helps.  The pH is more stable in that tank than
>in my other tank...

It's unlikely that the coral has any direct effect on buffering.

>I have soft water too, and thought that it was attributable to being from
>a deep >well that I *think* draws its water from close to its source since
>I live up high >(relatively). Am I way off base?  -I'm no scientist!

The water from a deep well is usually hard as it has had ample opportunity
to seep through the ground and pick up minerals.

>From Myongsu:

>I am interested in the possibility raised by Aaron with regard to the use of
>just CaCl and Mg (as MgSO4?) to buffer the water.  I have run across
>references to the use of increasing GH to buffer water; however, I have not
>seen any values recommended to reach a particular level of buffering/pH.  On
>the other hand, I have also read posts which state that buffering is a
>function solely of H+ and OH- ions.

Don't try to use a carbonate buffering system. Carbon dioxide will
equilibrate out of the system and you will not easily be able to maintain a
stable pH. Your basic buffer consists of a conjugate acid-base pair, which
is typically a weak acid and its conjugate base, for example, acetic acid
and acetate. In water you get:

   HA(acid) + OH- <> H2O + A-(conjugate base)

along with:

   H2O <> H+ + OH-

pH change is resisted in a buffer system as adding base or acid will change
the concentrations of HA and A- instead of affecting the concentration of
H+.

The pH of a buffer system can be calculated from the Henderson-Hasselbalch
equation:

   pH = pK + log([A-]/[HA]).

Be nice to your wife and maybe she'll tell you how to use it.

>Finally, as I am running my tests, the thought has occurred to me that I may
>be doing something bad to my tanks.  Does anybody know what the the Proper pH
>(Aq. Pharm.), pH Stabilizer (Jungle) and Acid Buffer/Alkaline Buffer/Neutral
>Regulator (Seachem) products contain as ingredients?  Chromatograph anyone??
>The only one that indicates any kind of content is Neutral Regulator which
>states "Contains phosphate buffers and conditioning agents" (to be fair, Acid
>Buffer/Alkaline Buffer both state they are phosphate free).  Jungle is helpful
>in stating "Not for use on food fish."

It should be a crime that the ingredients are not printed on the labels.
What they are trying to hide is that they are selling you a few cents of
industrial chemicals with fancy packaging for several dollars. I have no
idea what is in these, but the use of phosphate buffers is common because
they are safe, natural, cheap and have a large buffering capacity. Too much
will promote algae and plant growth and way too much is toxic.

- -Doug Brown
debrown@kodak.com