# [APD] Qs re dKH maintenance

```I'm setting up a 20 high with the standard pH controlled co2 injection setup
(and a super nice custom-built LED fixture)...  I'm dusting off some old
perl scripts... so I set the controller at pH 6.8 and want 25 ppm co2 and so...

\$ phco22kh 6.80 25
If the pH is 6.70 and the co2 is 30 ppm, then the KH should be 5.01 degrees.

...now say I measure dKH at 3... so need to adjust dKH up by 2 degrees...

\$ bicarb2kh 18 2
Adding 0.68 tsp of bicarbinate to 18 gallons of water will increase the KH by 2 degrees.

(1) Can someone verify the equations...

dKH = co2 / 3 / 10^(7-pH)

bicarb = (h2o/5.28) * delta_dKH

?

(2) Does that look right, as a weekly proceedure?

(3) I used "grocery store" baking soda for a few years but then had
misterious problems with water borne green algea (pea soup.)  What are
people using to increase carbonate hardness?  Medical grade sodium bicarb?
(What I see online is from holistic companies which makes leery about purity.)
The SeaChem product?

steve
--

#!/usr/bin/perl -w
use strict;
my \$ph = 6.80;
my \$co2;
if ( \$#ARGV == 1 ) {
\$ph = \$ARGV[0];
\$co2 = \$ARGV[1];
} elsif ( \$#ARGV == 0 ) {
\$co2 = \$ARGV[0];
} else {
print "usage: phkh2co2 [pH] co2\n";
print "  calculate dKH from pH and co2\n";
print "  default pH is \$ph\n";
exit;
}
my \$kh = sprintf("%.1f", \$co2 / 3 / 10**(7-\$ph));
print "If the pH is \$ph and the co2 is \$co2 ppm, then the KH should be \$kh degrees.\n";

--
#!/usr/bin/perl -w
use strict;
my \$gallons = 18;
my \$kh_change = \$ARGV[0];
if ( \$#ARGV == 1 ) {
\$gallons = \$ARGV[0];
\$kh_change = \$ARGV[1];
} elsif ( \$#ARGV == 0 ) {
\$kh_change = \$ARGV[0];
} else {
print "usage: bicarb2kh [gallons] DKH_INCREASE\n";
print "  calculate tsp bicarb required to raise dKH\n";
print "  default water quantity is \$gallons gallons\n";
exit;
}
my \$bicarb = sprintf("%.2f", (\$gallons/52.8) * \$kh_change);
print "Adding \$bicarb tsp of bicarbinate to \$gallons gallons of water ";
print "will increase the KH by \$kh_change degrees.\n";

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```