Took the pool test kit out to the pond this morning.
Total alkalinity >150ppm Total hardness >500 The HTH didn't specify unit of measure, but according to their chart it is very high. Ph 7.5
I've put ~125 ton of crushed limestone in the pond since I cleaned it out. It also gets the runoff from ~500ft of the lane to my house. Most years it takes ~50 ton of inch-base crushed limestone added to that section to keep it in good shape. Every time it rains hard enough to run off the pond gets a dose of ag lime.