"ML" wrote in message
et...
I have a 20g fresh water tank that is 3+ years old.
Our water is naturally soft and I have problems keeping the PH up. It
is a community tank and I would like to keep the PH around 7.0. It is
currently about 6.6.
I have done frequent water changes and I use a gravel filter to drain
the water.
The Nitrates are about 20 ppm.
I have a penguin bio filter which I change monthly and an Ehiem
canister filter left over from my 55g tank from years ago. The Ehiem
filter I clean about every 3 months. I cleaned it about 6 weeks ago.
Right now the tank is very clean.

3 weeks ago I added 4 fish and lost 3 of them plus 5 other fish.
I took my water into a fish store to be checked.
The PH is low which I know and so is the alkalinity.
A couple of years ago when I had PH problems before, I got advice to
add crushed coral and maybe some sea shells as a natural way to raise
the PH. This seemed to work for about a year. I recently added a few
extra sea shells to try to raise the PH.

Is there a natural way to raise the alkalinity? I am guessing that is
part of the reason why my PH is so low. The fish store folks are
trying to sell me some buffering chemicals which I want to resist if I
can.

Thanks,
Mark


Dolomite, aragonite, crushed coral, limestone, tufa, petrified wood, etc
will all add calcium carbonates, but may not solve your problem.
Minerals dissolve at variable rates, i) permeability which varies by
mineral, ii) exposed surface area, so limestone is much slower than
coarse coral, and iii) acidity of the water relative to it's natural
point of stabilization (so coral reacts to pH 7 more than limestone, as
it stabilizes at a higher pH)

On the other side of the ring, you have a force which is causing the
water to acidify (decaying organic matter in the substrate and the
filters), and the only thing keeping it in check is your water's buffer.

The sequence is as follows:
1) establish that the acidifying force is under control (clean filters,
and intense gravel vacuuming over a month).
2) if the pH stabilizes but the trend downward persists, add to the
buffer (baking soda) and then add natural minerals.
3) monitoring the pH and the kH, add & adjust minerals used and
positioned accordingly (for mild buffering, coral chunks, for heavy
buffering, as substrate or inside extra filters).

You can skip step 2, if the case warrants it (I usually do), but don't
skip step 1. Step 2 can be useful where the natural kH is under 2, and
then it just becomes an additive during water changes (but don't skip
step 1). The quantity & effort to dissolve enough minerals to
counter-act old-tank syndrome can be ridiculous, and the greater the rate
required for stabilization, the more precarious the operation of the tank
becomes. (jmo)

Mrgardener is right. These posts do come out preachy ;~).
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