I'm more inclined to have folks suggest the pH/KH table, then slowly ...........and like 1/20th of a turn of the needle valve each step, adjust it up from there and watch the tank closely.
We cannot say that 15ppm or 30 ppm is optimal, each tank will be different.
My tanks sit at 70 ppm and 55 and 50 ppm.
I adjust slowly and watch the plants, and the fish etc.
As long as I get more plant response and the fish are fine, I will add more.
I have good current and surface movement and high O2 levels.
So this counter acts any issues with high CO2.
My tap water has a KH of 1 degree or about 20 ppm.
So even if there's other non carbonate alkalinity in that number, it AIN"T much.
If you have a higher KH's, say 4-10 degrees etc, then you have a lot of potential room for errors in the assumption that it is all carbonate alkalinity.
This might be another advantage soft water users have.
I also use the volume per minute of CO2 to adjust things.
I bubble the CO2 into a large clear container, then time how long it takes to fill say 500mls, or some known volume. A measuring cup can work.
Then If I suspect anything changed, I can always use that as a reference.
the rate of CO2 will always be a stable reference, independent of the KH or pH, or drop checkers etc.
And it's free/cheap, easy to do.
I needed to change my old regulator for a new dual stage and wanted the same rate of CO2, this allowed me to do ti easily without having to go through the process of readjusting and watching for weeks to dial it in.
Dry ice, a sealed container with a pH probe rubber gasket sealed port and some reference KH solution can make a CO2 ppm water reference solution also.
Also, do not use the pH controller except for the day time only(eg, with the light timer).
Last edited by plantbrain; 02-03-2013 at 05:05 AM.