Inconsistent Alkalinity Test Results

Brian82143

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I have been having very inconsistent test results recently when testing my alkalinity. I use two different test methods: Hanna alkalinity checker with 1 year old testing reagent (expires 2023) and an API test kit (reagent expires 2024).

Two days ago I filled three vials for testing directly from the display tank and tested three times with the Hanna checker and got the following results: 7.4, 8.7, and then 7.7. I then tested with the API test kit and got an 11 as a result.

Today I tested twice at the same time with the Hanna checker and got 7.7 and 8.2. I tried the API test again and got a 10 as a result.

How can my results be so inconsistent? I am not sure what to believe in terms of my alkalinity levels which makes dosing a gamble at the moment. I know API test kits aren't the most reliable, so I am leaning more towards trusting the Hanna checker numbers but they have been inconsistent too. Anyone have any suggestions?
 

Pkunk35

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Sharing some of your method in how you use these test kits might reveal some inconsistencies that lead to those results.
for instance, I store the Hannah vials with RO water and empty them immediately before use as I find this keeps the tubes cleaner which is important because they measure light penetration through the sample I believe.
Maybe share some of your method and I’m sure things might pop up
 

gbroadbridge

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I have been having very inconsistent test results recently when testing my alkalinity. I use two different test methods: Hanna alkalinity checker with 1 year old testing reagent (expires 2023) and an API test kit (reagent expires 2024).

Two days ago I filled three vials for testing directly from the display tank and tested three times with the Hanna checker and got the following results: 7.4, 8.7, and then 7.7. I then tested with the API test kit and got an 11 as a result.

Today I tested twice at the same time with the Hanna checker and got 7.7 and 8.2. I tried the API test again and got a 10 as a result.

How can my results be so inconsistent? I am not sure what to believe in terms of my alkalinity levels which makes dosing a gamble at the moment. I know API test kits aren't the most reliable, so I am leaning more towards trusting the Hanna checker numbers but they have been inconsistent too. Anyone have any suggestions?
How long since you opened the Hanna reagent?

Once open its life does not much exceed 3-4 months depending on storage conditions.

Consistent test procedure is critical for those checkers as well.
 
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Brian82143

Brian82143

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Sharing some of your method in how you use these test kits might reveal some inconsistencies that lead to those results.
for instance, I store the Hannah vials with RO water and empty them immediately before use as I find this keeps the tubes cleaner which is important because they measure light penetration through the sample I believe.
Maybe share some of your method and I’m sure things might pop up
I rinse the vials in tap water after using them and let them air dry. I fill them up a couple times and empty them in the tank prior to filling up to the fill lines and dump about excess. I use a small pipette to suck out any excess water right before testing if they are not exactly at the 5 ml line.

Perhaps I should try keeping them in RO water as you suggested?
 
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Brian82143

Brian82143

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How long since you opened the Hanna reagent?

Once open its life does not much exceed 3-4 months depending on storage conditions.

Consistent test procedure is critical for those checkers as well.
I opened the Hanna reagent nearly a year ago and I didn't realize it had such a short life after being opened. Is it likely that the API test kit is giving me a more accurate idea in terms of alkalinity level (10-11) versus the lower results I am getting with the Hanna checker?
 

gbroadbridge

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I opened the Hanna reagent nearly a year ago and I didn't realize it had such a short life after being opened. Is it likely that the API test kit is giving me a more accurate idea in terms of alkalinity level (10-11) versus the lower results I am getting with the Hanna checker?
The results from opened Hanna reagent usually drops over time.

I'd expect after being open for 12 months it is essentially useless.

edit: Some folks in another thread are experimenting with storing in a refrigerator, which seems to extend the life.
 
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Brian82143

Brian82143

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The results from opened Hanna reagent usually drops over time.

I'd expect after being open for 12 months it is essentially useless.

edit: Some folks in another thread are experimenting with storing in a refrigerator, which seems to extend the life.
Yeah, I recently read about keeping it refrigerated. I will buy a new bottle and try keeping it refrigerated. Thanks.
 

MrGisonni

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Get new Hanna reagent. Change the battery on the tester. Rise vials with deionized water. Clean outside of vials with a microfiber cloth. Do yourself a favor and buy a measuring pipette so you can accurately measure out 10 ml Always line up the vial up in the tester the same way....face the 10 front. Get an alkalinity calibration kit from Hanna. Your results will be accurate +/- a few degrees. Good Luck! Hope this helps.
 

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taricha

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X-37B

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My Hanna egg reads an average of .5 higher for alk.
I use Salifert also and have not used Hanna in awhile.
If you get a test thats way off its most likely operator error.
When using Hanna I go through a bottle a month.
Salifert gives me accurate results and I use the low range and get around 200 tests per kit.
I also use Elos as a alk test backup.
Randys alk solution will tell you if your test method is accurate.
 

PatW

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I am not a fan of the API alkalinity test.

Hanna is fine. You can compare it to Red Sea Pro. Salifert will give a higher result than Hanna or Red Sea Pro by about .8 DKH, Any of these tests will let you know if the ALK is stable, trending upwards or trending downwards.

To be sure that the test are giving an accurate result, you have to calibrate them. To calibrate, you have to prepare a standard of known ALK. You can do that by getting some Bulk Reef Supply Soda Ash and mixing it up. Then take 1 gallon of RODI water and add enough of the BRS Soda Ash (BRS has a part of their web site (the calculator) that tells you how much to add to a known quantity of water to give a certain DKH. The Hanna test and the Red Sea Pro test are close enough to give you the approximate DKH and you really do not have to fuss with calibration.
 

Pkunk35

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I rinse the vials in tap water after using them and let them air dry. I fill them up a couple times and empty them in the tank prior to filling up to the fill lines and dump about excess. I use a small pipette to suck out any excess water right before testing if they are not exactly at the 5 ml line.

Perhaps I should try keeping them in RO water as you suggested?


Fwiw I found using tap here in Chicago left the inside of my vials with salt/mineral streaks especially if i let them dry. Now after completing a test, I rinse first with tap, then rinse with RO and then store with RO in them. Immediately before use on next test i shake them out 15 times to get most of the RO out and to make the process consistent. I use a microfiber cloth to clean the outside and I feel as if the cuvettes keep clean and last long doing this with no need to manually clean with a brush or their solution that Hannah sells (which I have and find very expensive).

also, as suggested, I think a auto pippette is a great idea (I just use a single syringe for all my 10ml measurements) bc I have read that the lines on the cuvettes do not match up to 10ml and if you line up enough Hannah cuvettes you will see that the 10ml mark is often times off.
 
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