What to make of these Alk results?

[Gribbles]

All tests performed using Hanna checker, same time of day and with a new bottle of reagent.

12/5 : 8.9
12/6 : 9.3
12/7 : 9.3
12/10: 9.6
12/11: 10.2

I was confused why my Alk is rising so much, so I immediately tested again with an entirely new sample.

12/11 #2 : 9.5

The only thing I'm dosing to affect Alk is 10mL of All-for-Reef
I also dose 10mL of vinegar early in the day
AWC 1gallon per day with Nyos salt that mixes to ~ 8.4
Tank has about 90gallons of total volume
pH swings from roughly 8 to 8.15
Salinity is at 1.026

Additionally, I'm very particular about how I test. I use a lab micropipette with new, disposable tips each time. One pipette for 10mL and another for 1mL. I wipe the cuvettes the same and even insert them into the checker facing the same direction. These tests should be as consistent as my hobbyist-self can provide.

My questions:
Why such an increase with such a small dose of A4R?
9.5 to 10.2 in back-to-back readings is quite the disparity imo. Even if this is within an acceptable range as to the accuracy of a Hanna checker, how can you trust and act on results like this?
Any suggestions on how to dial this in? I believe I'm already below the recommended starting dosage for A4R.

 

[Reefkeepers Archive]

All tests performed using Hanna checker, same time of day and with a new bottle of reagent.

12/5 : 8.9
12/6 : 9.3
12/7 : 9.3
12/10: 9.6
12/11: 10.2

I was confused why my Alk is rising so much, so I immediately tested again with an entirely new sample.

12/11 #2 : 9.5

The only thing I'm dosing to affect Alk is 10mL of All-for-Reef
I also dose 10mL of vinegar early in the day
AWC 1gallon per day with Nyos salt that mixes to ~ 8.4
Tank has about 90gallons of total volume
pH swings from roughly 8 to 8.15
Salinity is at 1.026

Additionally, I'm very particular about how I test. I use a lab micropipette with new, disposable tips each time. One pipette for 10mL and another for 1mL. I wipe the cuvettes the same and even insert them into the checker facing the same direction. These tests should be as consistent as my hobbyist-self can provide.

My questions:
Why such an increase with such a small dose of A4R?
9.5 to 10.2 in back-to-back readings is quite the disparity imo. Even if this is within an acceptable range as to the accuracy of a Hanna checker, how can you trust and act on results like this?
Any suggestions on how to dial this in? I believe I'm already below the recommended starting dosage for A4R.

Do you manually dose? If so that would explain the variation as that's what I usually see on my tank, though its throughout the day and not from the same sample. Also maybe try a different test to see how the results compare. Red Sea Alkalinity pro is my go-to with alk

 

[Gribbles]

Do you manually dose? If so that would explain the variation as that's what I usually see on my tank. Also maybe try a different test to see how the results compare. Red Sea Alkalinity pro is my go-to with alk

The A4R is dosed throughout the day with a Neptune DOS
I dose the vinegar manually (though I don't think vinegar plays a role in alk?)

 

[Reefkeepers Archive]

The A4R is dosed throughout the day with a Neptune DOS
I dose the vinegar manually (though I don't think vinegar plays a role in alk?)

I've heard mixed results with the Hanna alk and calcium with regards to accuracy. (IME Hanna hasn't been so reliable with me as I got a similar problem with my po4 test) though red sea has always given me consistent results

 

[SliceGolfer]

Has nitrate been trending downwards? Alk increases as nitrate lowers.

 

[Gribbles]

Has nitrate been trending downwards? Alk increases as nitrate lowers.

Nitrates were 56ppm according to an ATI ICP test from Nov 1

From a Nyos test:
12/3 : 50ppm
12/10: 40ppm

Indeed has been trending down. My understanding is a decrease of 15ppm across this timeframe would be mostly negligible on alk.

 

[Idech]

All for Reef also increases alkalinity in my tank. I do manual dosing once a day.

 

[Reefkeepers Archive]

All for Reef also increases alkalinity in my tank. I do manual dosing once a day.

Same, my LPS don't seem to mind the spike

 

[Gribbles]

Indeed I'm dosing it to manage my alk, so an increase is expected, but I'm using such a small dose and last night's readings leave me confused and frustrated

 

[Idech]

Indeed I'm dosing it to manage my alk, so an increase is expected, but I'm using such a small dose and last night's readings leave me confused and frustrated

How big is your tank ? I’m dosing 14 ml in my 75 gallons tank.

 

[rhitee93]

I believe Hanna lists the accuracy as being +/-0.3 or +/-5% of the reading. (I was looking at mine the other day)

5% of your readings would be ~0.5, so those measurements are really about the same.

Edit:
I looked it up again. My interpretation is 5% is the overall accuracy. Here is the link to the tester specifications:
https://www.hannainst.com/marine-alkalinity-dkh-checkerr-hc-hi772.html

 

[rtparty]

Size of dose doesn't really matter here. The fact that alkalinity is rising at the amount you're dosing shows you are dosing too much. Cut back to 7ml and see if the trend continues or reverses

 

[Randy Holmes-Farley]

I’d just cut back, or maybe stop dosing the AFR entirely. and see what sort of demand for alk you have.