Greetings from Canada. So a couple of weeks back I was gifted this beautiful looking dark rock with small white veins.......looked perfect for my planned iwagumi aquascape. I decided that I had better do the acid test (a few drops of API nitrate bottle #1) and wouldn't you know it, it fizzed and bubbled like crazy, indicating that these rocks would raise the PH. But since I struggle to keep a stable PH in my little nano tank (I have to put crushed coral in the filter), I though maybe these rocks would raise the ph to a tolerable level. So I put them into a small bucket with some water from our rain barrel. Pic #1 is the ph before adding the rocks. As expected, rain water is very soft and has a low ph. This was 4 days ago. Today I decided to test the water for the 1st time after letting the zebra stone sit in the water. Pic t#2 shows the results. Ph is sky-high and will probably continue to rise. As great as these rocks look, I think I'll stick with the dragon stone that I have and not deal with the high ph. Just thought I would share in case anyone else is looking to use zebra-stone.