My PH so far has been around 7.0, I check it about every three days. It has been the same since I started.

I checked the rain water one day for the hell of it, it was around 5.5 - and the ponds I have are all around 6.

The concrete I used was from an old chicken house my family had on the farm about 100 years ago. It's been sitting in the woods for a long time. I changed the filter medium to plastic cleaning pads this morning. Some folks suggested using oyster shells, which would change PH. Since the oil spill in the gulf oysters are getting scarce around these parts.