I have a new planted tank with co2 injection. My KH has been rising. A little over a week ago it was 5 degrees. We got back from vacation yesterday and found some algae in the tank... so today I cleaned the algae off, and did a 50% water change. The tap waters KH is 2 degrees. I retested today and it's 8 degrees in the tank several hours after the water change. My ph 6.6. Which according to the co2 charts is 60ppm. I'm wondering what could be causing the KH to rise, and if it's a problem? I put 10 shrimp in the tank yesterday, if that matters. Will start fertilizing tomorrow.