I picked up a ph controller for my calcium reactor and just for now put it in my sump last night just to display the ph for me. After calibrating it with the solution I put the probe in and after a while it was displaying 7.8 so I needed to top off anyways so I dumped some sea chem buffer for the water quantity into the bucket and let it top off. We went out for a few hours last night and came back and i went to see what it was and now it says its 8.8 at midnight. Wow thats high so let it be and this morning it is saying its 7.8 again. I test it and it looks like its 8.0 to 8.2. I wonder if this ph meter is not right ?

Any ideas advise on the matter would be greatly appreciated.

Thanks
Ryan