Alk Testing

[robmiller2]

I am curious as to accuracy of the two types of testing I am doing for my Alk. I have been using the Red Sea Pro test for Alk and my results were consistently 10-14. I recently purchased a Hannah Checker for Alk and my reading have been lower. Today I did both tests and the Red Sea was at 13 dKH where as the Hannah was at 9.9 dKH. Why such the difference?

 

[Randy Holmes-Farley Verified Community Expert]

One or both is wrong.

I can't say which.

 

[Alfrareef]

What salt do you use?

 

[Joe Grubbs]

I am curious as to accuracy of the two types of testing I am doing for my Alk. I have been using the Red Sea Pro test for Alk and my results were consistently 10-14. I recently purchased a Hannah Checker for Alk and my reading have been lower. Today I did both tests and the Red Sea was at 13 dKH where as the Hannah was at 9.9 dKH. Why such the difference?

@Randy Holmes-Farley has a good point...

I have difficulty in reading my Red Sea Pro Alk color endpoint and would perform as many as 3 tests to 'determine' what the Alk value was. So I shifted to the Hana Alk testing a year back. Both have a reputation of being reliable test kits. However, they will not read the same but should be close...

I'd encourage you to clean all your equipment and run a few tests with each. Being very careful with your processes and measurements. See if you can get some repeatable results with one kit or the other. Even still you may not have enough information to know which is 'correct' and you'll have to chose which you trust and go with it.

If you have access to a LFS many can run a test for you with their equipment...

 

[BadPanda]

I use red sea test kit as well. What I noticed is that when the color starts changing, mix it some more and see if it holds the color change. If no, ad maybe another drop or two till the color change holds. I've only been using it for about a month with great results. I bounce results with LFS that uses same kit and end up with same result. Been contemplating the Hanna kits but can't decide since I am getting consistent results. Try another test with both kits, then have another reefer or LFS run a test and see which one holds a truer result. Good luck with your endeavor.

 

[CindyKz]

Why not just get this

https://www.bulkreefsupply.com/hi75...rds-for-hi755-hanna-checker-marine-water.html

 

[Randy Holmes-Farley Verified Community Expert]

Why not just get this

https://www.bulkreefsupply.com/hi75...rds-for-hi755-hanna-checker-marine-water.html

It's not as useful as it may seem since it is not actually an alk standard, but just a color standard. All it checks is the light absorption measurement of the machine, not any errors from reagents, mixing, times waiting, scratches in the cuvettes, etc.

 

[CindyKz]

It's not as useful as it may seem since it is not actually an alk standard, but just a color standard. All it checks is the light absorption measurement of the machine, not any errors from reagents, mixing, times waiting, scratches in the cuvettes, etc.

Good to know thank you @Randy Holmes-Farley

 

[robmiller2]

What salt do you use?

Currently using Red Sea Coral Pro Salt, black bucket.

Why not just get this

https://www.bulkreefsupply.com/hi75...rds-for-hi755-hanna-checker-marine-water.html

I am definitely planning on getting this on my next order.


I will also being doing more testing with each to see about the consistency of each. I always thought that the Red Sea kit was high. The color would start to change to green then go back to blue, it can be hard to see the actual color change. The initial color change seems to be about what the Hannah reads.

 

[Alfrareef]

You should retest with Red Sea test and trust the result.
I don’t know why or if it’s a my bad feeling, but when i was using their Salt and reef program only with their tests I could get the results they advertised.

 

[Randy Holmes-Farley Verified Community Expert]

If you have a calibrated pH meter, you can determine the endpoint of an alkalinity titration by pH (see link below), then see what thee color actually is.

Or you can do a full DIY which is likely more accurate than a kit:

A DIY Alkalinity Test: By Randy Holmes-Farley - REEFEDITION
https://www.reef2reef.com/blog/a-diy-alkalinity-test-by-randy-holmes-farley