Kh testing- which test kit to trust

[DaveRaz]

Hanna measures 167 or 9.35dkh
Elos measures 7.5dkh

I've observed this variance between the two kits for the last 10 tests. What gives and which should I trust? Corals look fine but I want to know where kh really sits.

 

[Mark426]

Obviously one of them is wrong, but who knows which. If you want to know which one is most accurate then I see no other choice than to get a third kit. Salifert would be my choice.

 

[snorvich]

There are "standard" solutions available which have a predetermined value. Use one of those to calibrate your tests.

 

[DaveRaz]

Well I took your advise and tried a third test. I officially do not trust the Hanna any longer. This makes the third round of regents I have tried and all three have let me down.

Fwiw I ran a Red Sea pro test and it matched the Elos.

 

[cloak]

I have an API test kit, but I rarely use it... 7, 8, 9, 10 etc... Just as long as it's not getting there TOO quick...

http://reefkeeping.com/issues/subject/chemistry.php

 

[NewJack]

I had the same problem testing calcium.
I was getting 3 different results with 3 different kits. Red sea, salifert, and hanna
The Red sea and salifert were within 10% of each other, while the Hanna was no where close to what the others where reading. I calibrated the hanna with the appropriate test solutions and still same results.