I've been battling with my pH & KH since I set my tank up last Oct. Even with pressurized CO2, my pH would not budge from 8.5 I mixed in RO water over time and brought my KH down from 15 to 16 to 7. Last week, I finally made the switch from a trickle filter to a rena canister. What a difference that has made. Current pH is now 7! Gives me a C02 reading of 21ppm! I'm finally seeing pearling for the first time...