Hanna alkalinity test results

[dpfish]

I get about 0.8 dKH difference between the Hanna tester and my Red Sea test kit. Hanna is higher. I'm not sure which one to believe?? Any ideas?

 

[208reef]

0.8 difference just a single time or 0.8 difference consistently?

If just a single time, I would run each test method again 3 times, take the average of each method, and then compare.

Assuming the instructions are followed to a T, test vials are cleaned properly between each use (no staining on vial), and the outside of the vial is wiped with a dry soft wipe before it's put into the tester, the Hanna tester will be more accurate in my opinion.

Looking at the test procedure for both, the Red Sea kit requires a titration. If you don't add evenly sized drops each time or accidently drop a little past the color change, it could influence the results. With the Hanna checker, you add a set amount of reagent and then the photo cell gives you a result free of any color bias from the human eye. The other thing that makes me trust the Hanna tester more is that you can buy the calibration standard vials which would confirm your meter is accurate to +/- 0.3 dkH.

TL;DR: Spectrophotometer methods like Hanna are more accurate since you can compare to a calibration standard. Titration methods like Red Sea can be accurate if you have good consistent titration technique.

Here's a link to the calibration standard:

https://www.hannainst.com/hi772-11-marine-alkalinity-dkh-checkerr-hc-calibration-set.html

 

[VintageReefer]

0.8 difference just a single time or 0.8 difference consistently?

If just a single time, I would run each test method again 3 times, take the average of each method, and then compare.

Assuming the instructions are followed to a T, test vials are cleaned properly between each use (no staining on vial), and the outside of the vial is wiped with a dry soft wipe before it's put into the tester, the Hanna tester will be more accurate in my opinion.

Looking at the test procedure for both, the Red Sea kit requires a titration. If you don't add evenly sized drops each time or accidently drop a little past the color change, it could influence the results. With the Hanna checker, you add a set amount of reagent and then the photo cell gives you a result free of any color bias from the human eye. The other thing that makes me trust the Hanna tester more is that you can buy the calibration standard vials which would confirm your meter is accurate to +/- 0.3 dkH.

TL;DR: Spectrophotometer methods like Hanna are more accurate since you can compare to a calibration standard. Titration methods like Red Sea can be accurate if you have good consistent titration technique.

Here's a link to the calibration standard:

https://www.hannainst.com/hi772-11-marine-alkalinity-dkh-checkerr-hc-calibration-set.html

The calibration fluid verifies the tester is operating right, but there is no way to confirm the reagent is accurate. These can expire, they can degrade over time, become contaminated, bad batch, etc.

It’s still my method of choice especially for alkalinity, but I have seen bad reagents and wanted to add that to the discussion.

Additionally, the reading difference between each brand test kit has an estimated level of variance. An actual alk of 8.5 for example might read 8.2 on one brand kit and 8.8 on another brand