I have a 2500 gal pond that I established this past summer. I hv been regularly checking the ph and it has been running 9. I hv checked it in the morning as well as in the evening and get the same results. I used a lot of Limestone around the pond and the waterfall. Could that be the reason for the high ph level and if so what can I do to correct the problem. I have about 30 Koi in the pond. I use a test tube type test with drops. All other tests such as Amonia and Nitrates are all good. Any help would be much appreciated.