Different test kits, different readings

[DSenn]

I am wondering if anyone has used two test kits simultaneously and gotten different readings after testing the same source. In this case, I am referring to hardness test kits.

Right now I actually have 3 hardness test kits: Red Sea, Nutrafin and Aquarium Pharm. The Red Sea and the Nutrafin tests kits give the same reading, which differ from the reading I get from the Aquarium Pharm kit. For example, the Aquarium Pharm. kit gives me a higher GH reading and a lower KH reading than the other two.

Common sense tells me to use either the Nutrafin or Red Sea kits because they give matching readings, but I heard that the Aquarium Pharm. was 'the best' or whatever, so I am not sure which to go by. All the kits I have are new, so I would assume they aren't inaccurate due to age.

 

[Purrbox]

API is often recommended because you can get the Master Test Kit with liquid test kits at a reasonable cost. It's a good brand, but certainly not "the best". I'd recommend seeing if you can obtain a copy of the water report for your area. Compare this to your test results from the different kits. This would be an easy way to get a rough idea which test(s) are more accurate. Even better would be to obtain (make) a set of reference solutions. These have a known value, so which ever kit gives the closest readings is the most accurate.

 

[Innovator]

Understand that these tests and all tests in general have a degree or % of error so the same test may not show identical numbers, but at least should be in the "ballpark".