I have the Hanna Phosporous checker...love the ease of use and never having to guess the color or whether the color change is due to the light I'm currently in!!!
Alkalinity dKH
Alkalinity ppm
Phosphate Low Range
Phosphorus Ultra Low Range
All work great, Easy to follow directions, consistent readings between tests..s even when comparing the different meters and doing the conversations. Very interested in the Nitrite and PH checkers now.