Alkalinity differences

[collosalness]

Relative newbie here.

Apologize if this is not the right place.

I'm trying to figure out why i'm getting such different readings from hanna vs something like alkatronic.

For the hanna, (i think) uses a colorimetric method and i know dyes can sometimes go bad.

It's read anywhere from 8.4-9.2 dKH. This is in the setting of very low levels of All for Reef supplementation for a relatively new tank (1 month).

I am trying to set up a alkalinity monitor such as an alkatronic to read my tank alkalinity but it's reading much higher at 11.7 - 12 dKH
I've calibrated the pumps, the pH probe. I have made sure the reagent is mixed properly at a 1:4 ratio (using a scale).

I know the alkatronic titrates by adding a weak acid such as sulfuric acid. is it possible that the alkatronic is actually correct and the hanna is incorrect? I have used a brand new box reagent for the hanna with similar results.

I ordered the salifert, the second step is for me to titrate using the reagent on the salifert test with indicator to make sure that the reagent is actually correct.

 

[Randy Holmes-Farley]

When two devices disagree, one cannot know which, if either, is correct without testing a standard or using a third device.

Both methods are sound and do not disagree just because of the method used.

 

[collosalness]

Thanks,

I’ll have the salifert in a few days and check using that. Worse case I’ll order sodium hydroxide and make a standard to test…

 

[taricha]

I ordered the salifert, the second step is for me to titrate using the reagent on the salifert test with indicator to make sure that the reagent is actually correct.

this is my go to these days, - salifert to the "lavender" endpoint color that Jim illustrates here is very good.
https://www.reef2reef.com/threads/alkalinity-titration-endpoint-ph-salifert-endpoint-color.543556/

probably best you can do short of making your own standard.

 

[Faurek]

One might be testing carbonate alkalinity and the other total, read what the test kits say, I used to have an old case that tested both.

 

[Randy Holmes-Farley]

One might be testing carbonate alkalinity and the other total, read what the test kits say, I used to have an old case that tested both.

I’m not aware of any common test kits that read carbonate alkalinity. They all read total.

 

[Faurek]

I’m not aware of any common test kits that read carbonate alkalinity. They all read total.

It was some old stuff it read in meq/l, believe it was Kordon 15 years ago, felt like a scientist as a teenager, but it didn't matter because I only cared about macros and not corals.

 

[Randy Holmes-Farley]

It was some old stuff it read in meq/l, believe it was Kordon 15 years ago, felt like a scientist as a teenager, but it didn't matter because I only cared about macros and not corals.

The units of measure do not indicate the type of alk measured. I’ve been measuring alk for decades and folks should not be worrying about the type of alk measured by any titration method, which are all total alk. :)

 

[Faurek]

The units of measure do not indicate the type of alk measured. I’ve been measuring alk for decades and folks should not be worrying about the type of alk measured by any titration method, which are all total alk. :)

No, meq/l shows how far back it was, but it came with carbonate and total alk to test, also came with ammonia, nitrite, nitrate and pH. It used to be so cheap compared to today as well.

 

[Randy Holmes-Farley]

No, meq/l shows how far back it was, but it came with carbonate and total alk to test, also came with ammonia, nitrite, nitrate and pH. It used to be so cheap compared to today as well.

Well, I still use meq/L in many articles since it is far easier to do calculations with.

Some kits say carbonate hardness, but they are actually total alk tests. Like this one;

https://apifishcare.com/product/kh-test-kit

In any case, there is no titration test kit that is capable of measuring only carbonate alk in seawater. It is not the issue in this thread.