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# Re: [APD] Qs re dKH maintenance

```Hi Steve.

Your bicarb calculation should be mg bicarb = gal of water *
3.785L/gal * 30mg/dKH * delta dKH.  Depending on your baking soda and
how well you pack it into the tsp, you should have about 4.8g per tsp
of baking soda.

I think you excluding units in this calculation and using 5.28 is
confusing (but gets you pretty close.  Rule of thumb is 30mg baking
soda raises 1L by 1dKH, as per the formula above.)

If you want it, here's the Perl script for
http://dropcheck.petalphile.com.  I've set the marker to the dKH cals:
https://github.com/flores/dropcalc/blob/master/drop_calc.pl#L169 (also Perl)

More importantly, moving KH in your aquarium unnecessarily affects
your fauna (for example, Claus presented that the most stable
parameter in most places he measured in the wild was dKH and dGH), and
calculating CO2 from pH and dKH, as if there are no other buffers in
the aquarium, has proven to be inaccurate over the years.  Many
gardeners have found moving KH is more impactful than a relatively low
pH for *most* fish.  (Especially most any fish you'd ever have in a
planted aquarium.)

A popular alternative are drop checkers.  Drop checkers use DI/pure
water to remove the chance of any other buffer, then use simple pH
reagents to measure pH.  In such a closed environment -- unlike an
aquarium! -- the pH/dKH relationship becomes predictable, and you can
have more confidence in your calculated CO2 levels, though the color
of drop checkers adds some wiggle room there.  (
dropcheck.petalphile.com has some ideas for this, as well as using
drop checkers to calculate for any CO2 target. )

If you do use this method -- and I think you should -- keep in mind
you can still use your pH probe to automatically/programmatically
control the CO2 solenoid.

1) Use the drop checker to dial into your CO2 target.  Take your time with this.
2) Measure the pH in the tank.
3) Set the pH probe to shut off at 2's pH.

Just ideas and suggestions.  Nice to see a fellow Perl user on this list :)

On Thu, Mar 22, 2012 at 8:33 AM,  <rader at hep_wisc.edu> wrote:
>
>  > > (1) Can someone verify the equations...
>  > >
>  > >   dKH = co2 / 3 / 10^(7-pH)
>  > >
>  > >   bicarb = (h2o/5.28) * delta_dKH
>  >
>  > I made a calculator for this a few years ago in JavaScript. You're
>  > welcome to inspect the code and port it to Perl.
>
> http://fish.bakerweb.biz/calculator.js
>
> CO2_Out.value=round((3*KH1degrees.value*Math.pow(10,(7-pH1.value))),0);
>
> thanks.
>
> my perl scripts were included in m my previous msg after my sig.
>
> steve
> --
>
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