AquaForest Alklinity Test

[Peer.Boerner]

Not sure if this is the right forum so please forgive me if I’ve made a mistake. I decided to try the AquaForest Alklinity test instead of replacing my Salifert Alklinity kit. Thought I’d try something new. I’m sorry to say that I’m having a hard time determining the end color for the titration. The instructions say a bright pink color but the solution goes pink early in the process. I’m not sure how light is light enough pink. Anyone have any guidance here or experience with the test? Maybe a photo of what the end color should look like? The instructions have colors on them but they are in my opinion vastly different to what I see during the test.

 

[get-salty]

What is the reading right when it turns pink ?

 

[Randy Holmes-Farley Verified Community Expert]

Did you carry it further to see if there were more changes?

 

[Peer.Boerner]

Did you carry it further to see if there were more changes?

I did and it got somewhat lighter and then stopped changing. (I noted when I thought it stopped but kept going to see what would happen). I don’t like the word “somewhat” when doing an analytical exercise. So I was curious if people just go the dark initial pink phase and call it done or if I must go further.

I get the feeling a Hanna Alk checker is going to be in my future. Though I did like the Salifert color change more.

 

[Peer.Boerner]

What is the reading right when it turns pink ?

Well that’s the question. Which pink? The first “dark pink” it’s 7.7. The second lighter pink 9.3. I’m inclined to believe the 9.3 because I deliberately added sodium bicarb to my NSW batch to bring it to 9.0. I guess I’ve arrived at my answer. Just keep going until you think it’s bright pink. But. Don’t like that answer. Was hoping for something more concrete and clear.

 

[Randy Holmes-Farley Verified Community Expert]

You can always drop a pH meter into it if you have one. The color is just a way to indicate pH. I do not know how AF designed the test, and I don’t see that many people talk about using it, but my guess is that the first full pink is the endpoint.

 

[Peer.Boerner]

You can always drop a pH meter into it if you have one. The color is just a way to indicate pH. I do not know how AF designed the test, and I don’t see that many people talk about using it, but my guess is that the first full pink is the endpoint.

Thanks Randy! What would the pH value I’d be looking for?

 

[Randy Holmes-Farley Verified Community Expert]

Thanks Randy! What would the pH value I’d be looking for?

About pH 4.3.

 

[Peer.Boerner]

About pH 4.3.

Many thanks. I may try that and see. Now I’m very curious. I’ll share what I learn.

 

[Peer.Boerner]

Many thanks. I may try that and see. Now I’m very curious. I’ll share what I learn.

Here’s the first “red/pink” pH is 5.51 the second photo is bright pink and pH is 4.23. Note I didn’t freshly calibrate my probe so not claiming lab accuracy. Colors may be off due to camera settings. And as I look now the first isn’t as pink as I thought. Thanks for helping me learn about using pH to detect a titration endpoint.

 

[Randy Holmes-Farley Verified Community Expert]

Sounds good. You’re welcome.

Happy Reefing!

 

[Randy Holmes-Farley Verified Community Expert]

Fwiw, this has more:
https://www.reefedition.com/a-diy-alkalinity-test-by-randy-holmes-farley/

 

[MBruun]

I have used AF alkalinity test for a while. I find easier to read than Salifert as it change color within one or two drops, and it also matches the ICP-MS test results so I'm confident that it give me the right value.

The two pictures show the difference of two drops

 

[Peer.Boerner]

I have used AF alkalinity test for a while. I find easier to read than Salifert as it change color within one or two drops, and it also matches the ICP-MS test results so I'm confident that it give me the right value.

The two pictures show the difference of two drops

Thanks for sharing that. For me, I can’t see the difference clearly enough. I’m still a big fan of AquaForest, just not their Alk Test - because of my limited ability to see that color change.

 

[Slider162]

I also give it about 10 seconds between those last two drops. It will turn pink and then slowly drift back to purple. Once it stays pink for 10 seconds I stop.

 

[Randy Holmes-Farley Verified Community Expert]

I also give it about 10 seconds between those last two drops. It will turn pink and then slowly drift back to purple. Once it stays pink for 10 seconds I stop.

That delay is appropriate. :)

 

[Aquaforest]

Hello, determining the exact endpoint in titration can sometimes be tricky when you first switch brands. For the Aquaforest KH test, the transition goes from a blue-green color to a distinct pink. The "true" endpoint is reached at the very first drop where the solution turns into a clear, bright pink that remains stable after swirling the vial. If the color looks like a pale or "dirty" pink, add one more drop; if the color does not become a deeper pink after that extra drop, then the previous drop was your final result.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for the clarification! :)