Ballpark. I don't need 0.1 to equal 0.1. But if one reads 0.10 and the other reads 0, then there is some concern as those numbers can have vastly different results in coral health.
All good, I'm trying to get an expectation is all. One more question if you will. What model of Hanna tester(s) are you using? I read Hanna so assuming it is for both Phosphate and Nitrate. They have low range, high range, HIxxx, etc.