Hanna vs. Alkatronic

[Scottiemac]

To begin with, everything has been calibrated within the last three hours.
The reagent for Hanna is new. The reagent mixture for the Alkatronic is exact, new, and confirmed with a smaller test mixture.

My numbers are dramatically off between the two.

The issue started on Monday when I discovered that the Dosetronic had added 2200ml of alkalinity to the tank over the previous 40 hours. That day I received a new bottle of reagent concentrate.

Upon retesting with the new mix I was at 15.09 after the old reagent was giving me results consistently in the mid 8s. Hanna was giving me similar results, however the reagent I was using had been open for several months.

As the 15.09 from the Alkatronic seemed in line with having had 2200ml of Alk added over the weekend, it was assumed that the Hanna checker's reagent had expired and the Alkatronic was accurate.

Over the next few days the Alkatronic slowly dropped to what is now 9.04. Upon receiving a new bottle of Hanna reagent today, I calibrated and tested with that and received the 6.32 reading.

Now I don't know what to think. A difference of perhaps .5 kH might be explainable, but almost 3 kH?

Note that my Hanna checker is the ppm model (since I didn't read the packaging first) and I'm using the reagent for the dkH model. Hanna says this is the same reagent. I'm not sure why they don't just make one reagent; maybe they just like to confuse people for funsies.

Anyway, can someone provide some insight as to what is going on?

 

[Dan_P]

To begin with, everything has been calibrated within the last three hours.
The reagent for Hanna is new. The reagent mixture for the Alkatronic is exact, new, and confirmed with a smaller test mixture.

My numbers are dramatically off between the two.

The issue started on Monday when I discovered that the Dosetronic had added 2200ml of alkalinity to the tank over the previous 40 hours. That day I received a new bottle of reagent concentrate.

Upon retesting with the new mix I was at 15.09 after the old reagent was giving me results consistently in the mid 8s. Hanna was giving me similar results, however the reagent I was using had been open for several months.

As the 15.09 from the Alkatronic seemed in line with having had 2200ml of Alk added over the weekend, it was assumed that the Hanna checker's reagent had expired and the Alkatronic was accurate.

Over the next few days the Alkatronic slowly dropped to what is now 9.04. Upon receiving a new bottle of Hanna reagent today, I calibrated and tested with that and received the 6.32 reading.

Now I don't know what to think. A difference of perhaps .5 kH might be explainable, but almost 3 kH?

Note that my Hanna checker is the ppm model (since I didn't read the packaging first) and I'm using the reagent for the dkH model. Hanna says this is the same reagent. I'm not sure why they don't just make one reagent; maybe they just like to confuse people for funsies.

Anyway, can someone provide some insight as to what is going on?

Unless you are testing both methods with a standard, you won’t know what is going on. Both methods could be off. Average the results until you obtain an alkalinity standard or using a pH meter to detect a 4.5 endpoint, titrate the aquarium water with 0.1 N HCl.. An alternative is to use the Red Sea titration kit. I found it agrees well with titration.