Originally Posted by Beasts
is there a meter that measures CO2 concentration in water?
CO2 sensors. You can measure CO2 right above the water to determine the CO2 in the water or you can water proof the Sensor and use a CO2 permeable membrane and submerge it in the water. The underwater CO2 sensors are used by scientists and cost thousands of dollars.
You can use a drop checker with a controlled kh solution to give you a decent estimate of CO2. The ph , kh, co2 relationship does work in a controlled environment like a drop checker.
As long as your plants are growing and pearling, go with it, as long as the fish don't die from OD.