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Re: HCL dosing

> Date: Sat, 28 Oct 2000 20:55:17 -0500
> From: "Len Kutz" <len at kutzfamily_net>
> Subject: HCL dosing
> I recently purchased some 20% HCL and have been dosing a small amount every
> night trying to lower the ph of my tank.  It is a 75g tank with tap water
> that is about 8.25 ph, 100+ ppm GH and 120+ ppm KH.  For the past 4 nights
> I've added 15-20 drops of HCL to the sump.  Every night I measure the ph
> before putting in the HCL and about 2 hours afterwards.  Every evening
> before putting in the HCL the ph has been up to or very close to 8.25, but
> after adding the HCL the ph drops to about 8.  I'm concerned about dropping
> the ph to quickly, but I didn't expect the ph to keep going back up so much.
> Am I doing something wrong or is it the buffering of the hard water causing
> this?  Should I put in more HCL?  Any suggestions would be appreciated.
> I've been very cautious doing this and so far none of the fish or plants
> show any signs of problems.

Yes, it probably is because of the buffering, but you apparently don't
understand what you are doing enough for this process to be very safe.
Another source of pH stabilization is the substrate material. If it contains
shells, limestone, marble or dolomite, adding acid just dissolves a little
more each time. Around here, our best-looking gravel, "Lapis-Lustre" by
RMC-Lonestar, is just loaded with shell chips. Wonderful stuff for the
Ca-deprived waters of SF and Alameda-Hayward, but despicable in our
hard-water areas, like San Jose and Santa Clara.

100 ppm GH water is *not* considered hard, at all, BTW. It is rare to see KH
higher than GH in natural waters. It usually takes sodium bicarbonate (o/e)
to do that, and that is pretty rare in natural US waters.

Why on earth are you struggling to lower the pH so hard? Unless you have a
serious ammonia problem (highly unlikely in a well-planted tank), I can see
no earthly reason to try to destroy all your nice buffering by adding a
strong acid.

Fish and plants usually don't care too much about absolute pH, and there is
certainly no such thing as "pH shock." Stores advise beginners to keep the
pH between 6.5 and 7.5 because nitrite kills fish at low pH and ammonia
kills at high pH. They know from experience that newbies won't have dense
enough plantings to absorb all the nitrogenous products that the overstocked
fish will produce. [This is the source of a lot of the BS about "cycling,"
too. Bacteria *can* convert the nitrogen-containing compounds to a far less
lethal form -- nitrate.]

The markup on pH kits is also fierce. Compare the same exact solutions in
the pool dept. at Home Depot, to see what I mean. The LFS knows the kits are
"easy money." 

"Magic" always sells very well to the uninformed.

pH measurement *is* useful in planted tanks with CO2 injection, because
measuring the buffering level (KH), and how much the extra CO2 causes the pH
to drop, can give a really decent measure of the total dissolved CO2. The
absolute pH value, between about 4 and 10 is fairly unimportant in any
otherwise healthy tank.

The traditional "pH crash" when all buffer is exhausted is usually utterly
harmless, unless the acid is coming from heavy decay products that are, in
themselves, quite toxic at low pH (such as those with nitrites).

One last pH problem. Lead plant anchors and other metals like copper *can*
slowly become lethal at low pH because they are much more soluble there.
That's why EPA has mandated that tap water in areas with older houses must
be raised to around 8, to keep from leeching out the lead from solder joints
and the copper from the pipes. [Most places, they add lime or other strong
base to do that, but yours could be adding sodium bicarbonate, a more
permanent (buffering) approach to the problem. IDK.]


PS. This note was another example of the value of including some kind of
location in any messages to plant and fish lists. These phenomena are
usually regional. "Seltzer" springs aren't common. You don't often find
"Lapis Lustre" in Boston. We learn a lot by knowing "where."


Wright Huntley, Fremont CA, USA, 510 494-8679  huntleyone at home dot com

         "Ignorance creates a fertile climate for demagogues;
         maybe that's why politicians give so much support to
                the public education establishment."
                                              Walter Williams 
               *** http://www.libertarian.org/ ***