Very Valid point!! IDN what I was thinking - I have API test kits but the PO4 test is very vague and the lowest reading is .25ppm - I try to locate a used one for sure
You must run up the escalator at Sears backwards and naked while singing " I am the queen of France" and simultaneously trying to eat your own head with a plastic spork.
Thought I posted this but I will try again.
I have the Calcium Hanna Checker Calibration kit, if anyone is questioning their readings I will be happy to check your meter with the kit.
They work good, I got all 3 recently and they are easy to use, the calcium is a bit of a pain requiring ro/di water to 0 it out but the other 2 are very easy to use and accurate