Review on 📏 Precision Calibration for Hydroponic Systems and Aquariums by Jim Cox

I just bought and calibrated it. I thought my pond water was high at 8.57 but we had fluctuations in our tap water so I wanted to bring it down a bit with acid. Instead I decided to check the calibration to check their pH and it was 8.76 so I tested the tap water and it was pretty much the same! So I mistook the 6.86 calibration solution for the calibration, but it kept flashing until 9.18! I messed up the 4.01 and it worked fine, but then I messed up the 9.18 solution and nothing else registers as 0.00. I'm so thankful I checked this out because if I lowered the pond any further my fish would no doubt be dead by morning. It was only a 5.4 when I finally tested it with a good multimeter. I will never buy this variety again! I just buy the cheap ones and throw them away when they start to shrink in size, not relying on them!