| | Re: Water management advice needed
The way to get CO2 in the water is to add it. No chemical or chemicals you can add will increase the CO2 in the water. Excel adds an organic chemical that the plants can use as a source of carbon, but not nearly as well is they can use CO2.
Any CO2 in the water lowers the pH. The more CO2, the lower the pH. The higher the KH, the higher the pH, but CO2 still lowers the pH.
The pH of the water is not an important parameter. It is the total dissolved solids in the water, and/or the GH and KH that affect the fish. Those should be kept about the same all the time - no sudden increase or decrease.