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[APD] Strong acids, peat, and tempermental plants

I believe originally the question of whether it is possible to remove KH
using strong acids, or not, was asked in relation to growing plants that
seem to only do well in soft water in tanks containing a peat like

On the subject of strong acids and lowering KH, I think this can be done by
someone who is careful enough, but safety issues aside, it can be a real
pain.  I am a chemist by profession and am perfectly comfortable using
reactive chemicals and I wouldn't bother.  The problem is that you want to
change the buffering capacity of a solution that is only weakly buffered.
So knowing how much acid to add *is* an issue.  As previously mentioned, you
will have to let the dissolved gasses in solution (part of the buffer
system) come to equilibrium, which will depend on both air and water
temperature.  So what will happen is you will then have difficulty
"removing" KH without lowering the pH too much.  And you will be measuring
the pH constantly, which may not be an issue if you have a meter.  Since you
are not actually removing any ions, only reducing buffer capacity, I don't
see why the plants should care at all.  And you are adding other ions,
chloride for example, which may have an effect.

Perhaps it's the humic acids from the substrate that are having the effect.
After reading the many posts at the Krib on the beneficial effects of peat
on plants and fish I decided to try using peat-treated water.  I had to do
something because my local water, which is natively soft and slightly
acidic, is treated with base to raise the pH to 8.0 (to protect the copper
piping).  I don't want to do RO because of the waste factor (my water is
unreasonably expensive) and I was thinking of doing discus at some point so
that might matter.

So if it might be the humic acids from the peat-like materials that are
beneficial to nutrient uptake in the plants in question, the the method I
use for peat-treated water might be of interest to you.  Below is how I do
it and some comments on using peat in general that I did not find on the
Krib.  It's very inexpensive and takes relatively little effort although not
as little as RO.  This system lets me get about 120 gallons of change water
for about 10 minutes of actual effort in setting up.  This is two weeks
worth of water for me.  Of course, if you have harder water, it will work
less well.

The two common methods of using peat that I see are standing water in a
barrel with peat in a nylon bag and putting peat in an aquarium filter.
Putting peat in a filter is not an option for me since I only use a canister
and do not want to open it up every week, not to mention that your water
parameters will change over time because initially there will be a large
effect and then it will taper off.  Soaking in a barrel also did not work
for me-- the water got really dark but the pH didn't go down as much as I
wanted.  The dark water was pretty cool, I couldn't see 12 inches into my
tank except for the beady little red eyes on my head and tail light tetras.
But the light attenuation in a planted tank isn't exactly desirable.  So I
set up what a chemist would call a chromatography system--more or less like
putting peat in a filter, but doing it in a barrel rather than
in the aquarium.  In a nutshell, it's a PVC pipe packed with boiled peat
through which I flow water into a barrel.

Take a 12 inch long piece of PVC 4 inches in diameter and glue a cleanout
(threaded cap) on one end and a solid cap on the other.  These materials,
including glue are about $20 (US).  Drill holes in both ends of a diameter
that will allow you to press fit a piece of vinyl tubing.  This is called a
column.  You could glue in barbed fittings, but I would break them causing
more effort...  What I do is force vinyl tubing into the interior of the
column, wrap the end of the tubing a couple of times with teflon tape and
pull back through (out) until tight.  Do this on both ends and you have a
functional chromatography column.

Now you need to put the peat in the column.  You need to put something just
inside the column outlet that will hold the peat in.  I use filter
floss--couldn't be simpler.  Now you could just put peat right in but that
isn't very effective.  Peat holds a lot of air and just running water
through will fail to remove alot of it.  To get the air out, I boil the peat
first.  Put about 1-1.5 gallons of loose-packed peat in a bucket.  Then pour
2 gallons of boiling water in the bucket, stir, cover loosely and let sit
until cool.  I do this outside--peat stinks, and boy would it be bad to have
a bucket containing boiled peat fail in the house!  Even if it's below
freezing, I do this outside.  I let the peat settle, usually overnight, then
pour off the water.  This is probably similar to blackwater extract so it
might be of interest to you, I discard it.  Then I pack the peat in the
column, screw on the cleanout (inlet) end using a little teflon tape there
too, and hook up the inlet to the faucet.  I run the first half gallon or so
to waste but until the really dark water has passed, again this may be
blackwater extract that you might be interested in, then just *secure* the
outlet in a barrel.  The column leaks a bit, I just sit it in a
bucket--after making more than 100 gallons it doesn't leak even half a
liter, so I don't care.

Flow rate matters.  There are two things going on here.  One is ion
exchange--the 'softening' process.  The other is organic extraction--the
leaching of humic acids and similar materials into the water.  Both
processes result in acidification.  Only extraction gives the color.  Both
processes are less effective the faster you force water through the bed of
peat.  That is, the slower you run water through the column, the darker and
more acidic it will be.  I run it at about 5-10 gallons per hour.  So about
$0.25-$0.50 worth of boiled peat takes about 120 gallons of pH 8.0 tap water
to below pH 6.0 on my pH scale.  Oh, and the difference between boiled peat
and not is 5 fold--unboiled peat will only get you about 20 gallons.  I then
add baking soda to bring the pH (and KH)  to where I want it so that when I
inject CO2 I get pH 6.8 in my tanks.

One note of caution, if I run this water directly into my aquaria my zebra
otos (Otocinclus cocama) start dying.  (Darn things are expensive too.)  My
Bolivian rams, cardinals, corys, miscellaneous tetras, and Amano shrimp
don't seem to care.  And no, I didn't forget to add dechlorinator, which I
don't otherwise do.  I have proven this to be true on two different tanks.
I have no idea why this is so...  Could have been the dechlorinator for all
I know.

Anyway, this is a really cheap, relatively fast way to peat filter a large
volume of water.  If you do what I described, you'll get both the peat
filtered water which is only barely colored, and the 'blackwater extract' if
that's what it is.  You might try either in a tank without the
peat-containing substrates to see if it makes a difference to these
difficult plants.


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