Which alkalinity tests are accurate?

Reef Puncher · Jun 21, 2025

Hey. I bought a hydros IV. In order to get automatic testing done i have to pick an offset to set it to. At 0. It’s saying 8.4

Now the issue is my Hannah is showing 8.7.
My Red Sea is showing 8.8
My salifert is showing 9.9
My icp from last week showing 9.1

What the heck do I do with that information? I’ve been using my Hannah almost exclusively for past 2 years. Should I match that since it’s stabilty that’s more important than a number? Why is salifert so off?

RoanokeReef · Jun 21, 2025

I would go with Hannah, salifert is off probably due to what you perceive as the end color.

Garf · Jun 21, 2025

Reef Puncher said:
Hey. I bought a hydros IV. In order to get automatic testing done i have to pick an offset to set it to. At 0. It’s saying 8.4

Now the issue is my Hannah is showing 8.7.
My Red Sea is showing 8.8
My salifert is showing 9.9
My icp from last week showing 9.1

What the heck do I do with that information? I’ve been using my Hannah almost exclusively for past 2 years. Should I match that since it’s stabilty that’s more important than a number? Why is salifert so off?

Dunno, but I've made Randy's DIY alkalinity reference solution and it appears to indicate that my Salifert reads 0.5DKH lower than reality, lol.

You could try this;
https://www.reef2reef.com/threads/diy-alkalinity-standard.714738/post-7398778

VintageReefer · Jun 21, 2025

The key with alkalinity is stability

So if you’ve been using Hanna for 2 years and have been going by its results, then calibrate to match the hanna

This way of you second guess the automated testing you have a stable reference that your tank is used to