Why is Ph climbing?

[waterbear]

When you inject CO2 for "pH control" you are implying that there is some sort of pH drift (demand) already that you are trying to counteract. Since injecting CO2 makes the pH drop, the implication is that you have something else in the aquarium that is trying to make the pH rise (i.e. is basic or alkaline). So the combination of adding CO2, which just makes the pH drop, plus this basic source, causes the pH to be stable (or to drop less) and for the alkalinity to increase.

CO2 injection is used in aquariums (usually freshwater live plant tanks to promote growth) and also used in commercial pools for pH control. The net effect in both cases is a rise in TA

Richard

just for clarification here are some links of commercial equipment
http://www.brockent.com/CategoryView.asp?CategoryId=377
http://www.poolequip.com/Merchant2/m...egory_Code=CO2
http://www.aquasol.com/co2_systems.htm

If you read the info on the links they blame the rise in TA on the size of the CO2 bubbles injected.