Most reliable Alk testing?

[hatfielj]

I've been using Hanna tester for Alk almost exclusively since I started my tank 5 months ago. But, I have a Salifert kit as well to occasionally double check my Hanna results. The last few days I've been struggling to keep alk stable as I've had some issues with my salinity being low from my continuous water change pumps being mis-calibrated so I decided to check both Hanna and Salifert today.

Hanna is reading 8.4
Salifert is reading 9.3

That's quite a difference between the two. My salinity is currently sitting at 1.0248. I'm doing extra water changes to get it back to where I previously held it which was 1.026. I'm checking that with a high precision hydrometer, so I know my salinity reading is spot on.

Could the lower salinity be messing with my alkalinity testers??? If so, which one is more accurate?

Also, what is the best Alk tester/test kit out there these days? Is there a consensus? Given how important Alk is, I'm willing to pay more for a kit that I can really trust if one exists for hobbyists.

 

[Randy Holmes-Farley Verified Community Expert]

The salinity difference does not matter.

If you ask what is most reliable and accurate, my answer is a diy alk test using a pH meter and a standard acid. It is cheap and easy and very accurate (assuming the acid you buy is accurate). That is what I use, and is how a science lab would determine alkalinity.

https://www.reefedition.com/a-diy-alkalinity-test-by-randy-holmes-farley/

 

[RobertK]

I've been comparing Salifert and Hanna alk readings recently as well. The Salifert has been consistently reading 0.3-0.5 dKH higher than the Hanna for me.

 

[JonasRoman]

Tiration test I would say is superior over the method that Hanna uses not titration. There are definite weaknesses with that method, but it is very simple. So, a well performed titration test with brand new reagent, I would say is much more reliable than a Hanna Checker because it's based on the standard method. Then which brand you use has no importants as all ph-based titration tests are similar. As Randy says the best is of course to titrate with help of pH electrode because the colour change of pH reage is not as exact as an good calibrated electrode. The end titrationhould be round 4.5 maybe you little lower for 4.4 and one common reagant is bromocresolgreen that has a switch around that area.

 

[gbroadbridge]

I've been comparing Salifert and Hanna alk readings recently as well. The Salifert has been consistently reading 0.3-0.5 dKH higher than the Hanna for me.

If you titrate until the color change is complete Salifert does read 0.3 to 0.6 high compared to a standard test. Always for me over the last 5 years.

I stop at purple.

 

[JonasRoman]

If you titrate until the color change is complete Salifert does read 0.3 to 0.6 high compared to a standard test. Always for me over the last 5 years.

I stop at purple.

I think it's a very common overtitrate some because the color change is difficult to evaluate, and also will not happen exact on pH4.5, So your findings seems similar as many users.

 

[RobertK]

If you titrate until the color change is complete Salifert does read 0.3 to 0.6 high compared to a standard test.

I think it's a very common overtitrate some because the color change is difficult to evaluate

Thank you for that. I do titrate until the color change is complete. The reason I'm switching from Salifert to Hanna is that I have difficulty determining the color endpoint. I've only been testing both side by side as I transition to Hanna.

This suggests that my Hanna results are fairly accurate. Because I'm in the 7-8 dKH range I've been going with the Hanna numbers, as in that range I'd rather err on the side of alk being higher than my test kit indicates.

 

[JonasRoman]

As a curiosa I did a test, titrated with salifert and stopped at 3 different colour stages, and then measured pH of that with an electrode. The 2 last end points that I thought was correct had a pH of 4.0 and 3.5,meaning I was titrating too far. So the very first sign of colour change is the correct one for at least salifert. I would guess most user get around 0.3 dKh too high with salifert and probably many similar tests due to this very common overtitration. BUT, as long as you do same, this ofcourse doesn't matter, as its the consistency we want more than accuracy, as long as accuracy is within approx 0.3-0.5 dKH AMI.

 

[RobertK]

Well I've been performing the Salifert test the same way for the last 20 years, titrating until the color change is complete. I was taught in a college chemistry class 40 years ago that when doing colorimetric tests you should titrate until the color change is complete; I guess my lab instructor was wrong about that!

I repeated my Salifert test just now, also titrating to 3 different color stages. I got readings of 8.0, 8.3 and 8.7 dKH, with 8.0 at the first barely discernible color change, 8.3 when it switched from blue to pink, and 8.7 when the color change was fully obvious. A Hanna test done at the same time read 8.0. So Jonas you are correct (and I think Randy has stated the same thing previously). I'm going to stick with the Hanna test as it is easier to perform, but good to know it correlates with the Salifert.

OP can you try this too? You might be overtitrating with the Salifert test.

 

[Na_Shenas]

Hannah for alkalinity for sure. It’s accurate, fast and simple. You can find them used 25-50. Just as good.

 

[NeMoo]

I have an extra one, it is working and in line with my other one but I got it for a good deal and needed reagent lol. Would trade for anything interesting or useful

 

[X-37B]

I have found over the last 3 bottles of Hanna that alk readings increase when the bottle has 1/4 left.
Salifert is my backup with Red Sea as a third.
I watched alk go from 8 to 9 over the last few days.
Today 160-8.9.
Pulled Salifert 7.7
Red Sea 7.8
Got a new bottle of Hanna and alk is 7.7.

Note: I use Hanna multiple times a week. A bottle lasts maybe 2 across 4 systems.

Anyone else notice this?

 

[Project1004]

I use to use Hanna alk Tester as main one. I currently have two (bought new one at 2yr mark). They always give same results. Older one giving +0.6-0.4… NEVER DEVIATES.

Until few days ago, I wasn’t sure if I should trust Alkatronic because it was about 3dKh higher alway.

I had to add new reagent and decided to recalibrate it. (*im getting better at this*)

And now my Alkatronic reads about the same as Hanna’s. +0.3…. Use to be +2.0…

It was my own fault Alkatronic was testing at higher than it was. My measuring conversion was off by a lot.

So I’m still using Alkatronic as main (testing 4 times but was at 2 times due to new thing I’m doing to my tank).


This morning (O=old N=new). Same vial with same water source

Alkatronic was giving too big of differences lately. Calibrated while adding reagent.

Idk about the pH. It’s all over the place. Also noticed slots of white film forming inside of the test flask. X.X

 

[Kene]

Adding my test results using Hanna n Salifert

Hanna(new bot-exp 12/26) = 6.7; Salifert(new-exp 4/28) at 7.7.
Unsure which to trust at this moment.
I am seeing a variation of 0.6-1.0 btw the 2 at times.

 

[gbroadbridge]

Adding my test results using Hanna n Salifert

Hanna(new bot-exp 12/26) = 6.7; Salifert(new-exp 4/28) at 7.7.
Unsure which to trust at this moment.
I am seeing a variation of 0.6-1.0 btw the 2 at times.

I would trust the Salifert if you stopped adding titrant at the correct point which is slight purple or just changed to pink.

Most people go too far as they go too fast and dont swirl for long enough between drops resulting in a reading about 0.6 too high.

If it's gone total pink you have definitely gone too far.

 

[PharmrJohn]

Hanna for choice one and Salifert for choice two.

 

[killerkukoo]

The salinity difference does not matter.

If you ask what is most reliable and accurate, my answer is a diy alk test using a pH meter and a standard acid. It is cheap and easy and very accurate (assuming the acid you buy is accurate). That is what I use, and is how a science lab would determine alkalinity.

https://www.reefedition.com/a-diy-alkalinity-test-by-randy-holmes-farley/

this link no longer works. Ive lost faith in my hanna checker. id be very interested in learning the dyi way. do you have another link?

 

[JonasRoman]

this link no longer works. Ive lost faith in my hanna checker. id be very interested in learning the dyi way. do you have another link?

Let me just step in and ofcourse definitely agree with Randy.
Hanna is not using a standard method, they just add a fixed amount of acid and that gives a certain end pH depending on original alk. There is plenty if weakness in that method, like original start pH (co2 content), alk level, as the pH response of a fixed amount acid is not a linear graph and thus such a tests accuracy is very variable.

Acid titration tests are the way to go. In best case with an pH electrode to determine(most machines uses this) end titration point or colour indicator (most manual tests and some machines )

Jonas

 

[Randy Holmes-Farley Verified Community Expert]

this link no longer works. Ive lost faith in my hanna checker. id be very interested in learning the dyi way. do you have another link?

Here’s the way back machine version:

https://web.archive.org/web/2020042...a-diy-alkalinity-test-by-randy-holmes-farley/