Ph increases

[Ronfire]

What would cause the ph in a pond to increase. It used to be 6.5 now it is 8.5 in 3 months?
all other tests looked good. I think gh was 17. I dont know the KH. thought the test kit had it as well but it did not.

 

[Ronfire]

Cant seem to edit the original post. KH test was 17% dont have a gh test. Just tested the well water and found the ph changed in that as well The increase has been from the water changes.

 

[JRS]

Glad you figured it out. The city water "liquid rock" in my area is always has a high pH and very hard. At least it is stable though. Our state DNR has a publication that goes in depth regarding pH and hardness, alkalinity and buffering. Page 7 also mentions photosynthesis as a pH increaser.

https://dnr.wi.gov/regulations/labcert/documents/training/basics-genchem.pdf