Test results different

[Ento-Reefer]

I started ATI elements about 3 weeks ago so I have been testing my alk everyday between 8-10pm.
Last night I got a reading of 7.5 dkh and since I had just increased my dosing by 5ml I expected the result to be equal or greater then the night before which was 7.7. My goal is to keep alk steady between 7.7-8.0. So I tested again, and then also using API, and some new reagent for the Hanna. These were my results:

Hanna- old but still good reagent
7.5
8.2
7.8

API
6.0
6.0

Hanna- New Reagent
7.6
7.7

Is this amount of difference between tests normal? This is the first time I have double checked my results. I am not sure if I should just take the average of the Hanna results or not? The API seems low, but then again it only gives you 1 dkh differences, I am inclined to believe the 8.2 result was testing error probably on my part.

 

[a6walter1]

I would first like to address the Hanna checker itself. If you look at their website, and scroll down to specifications, you will notice that the accuracy is ±0.3 dKH (if you have the dKH version). So, your "old but still good reagent" results are within the advertised tolerance.

Secondly, don't get so fixed on achieving that "perfect" number. Consistency is the key in reefing.

Next, I wouldn't trust the API results as far as I could throw them. There are many factors involved with performing and reading that test.

My advice for you is to keep using the Hanna checker, pick a number (for instance 8 dKH) and try to keep the test result within ±0.3 dKH (the accuracy of the checker).

 

[Ento-Reefer]

I would first like to address the Hanna checker itself. If you look at their website, and scroll down to specifications, you will notice that the accuracy is ±0.3 dKH (if you have the dKH version). So, your "old but still good reagent" results are within the advertised tolerance.

Secondly, don't get so fixed on achieving that "perfect" number. Consistency is the key in reefing.

Next, I wouldn't trust the API results as far as I could throw them. There are many factors involved with performing and reading that test.

My advice for you is to keep using the Hanna checker, pick a number (for instance 8 dKH) and try to keep the test result within ±0.3 dKH (the accuracy of the checker).

Thanks. This is what I was looking for. I haven't used the Hanna checkers before so I wasn't sure what the accuracy was. Sine my tank is relatively new and switching over to new additives I am trying to prevent wide swings. I know the demand will be increasing so I want to stay on top of it.