Lamotte, Red Sea, Salifert ALK Tests Evaluated

[David S]

Greetings All,
About a year ago I did an evaluation of Red Sea and Salifert Alkalinity Test kits.
Since that time there have been certain changes made to both kits, so I felt a reevaluation would be in order.
I am also including the Lamotte test kit. It's touted as being extremely accurate and, not surprisingly, more expensive than other test kits.
I should point out that all test kits were purchased within the last 3 month's and have expiration dates that exceed 2 years.
So what is different?
First the Red Sea - The previous test had a color change that was difficult to nail down. However, the current test has a clear color change from blue/green to green. The initial change can be subtle, but is noticeable.
There is also a yellow color which indicates going beyond the endpoint.
As for the Salifert - The endpoint was achieved by sort of a lavender coloration. The current kit has a photo of the endpoint and it is clearly pink.
Similar to the Red Sea test, the Lamotte has an endpoint color of deep purple and a past endpoint color of pink.
So for the last few weeks I have taken a total of three tests for all 3 kits.
Before I discuss my findings, I should explain how I determined the final result for each of the 3 tests.
Salifert - Observed the first sign of pink (light shade) and used that as my endpoint.
Red Sea - Used first appearance of green (absence of blue) although green color might persist for a few drops before turning yellow.
Similarly, there is somewhat of an overlap between the deep purple and pink coloration for the Lamotte test.
For the purpose of the test, I used the 1st drop where pink was noticed - although after shaking the sample the color would revert to the deep purple endpoint. Similar to the Red Sea test, this could persist for a few drops before turning completely pink.

Final Results
In all 3 testings the results from the Lamotte and Red Sea test kits were virtually identical.
In each case the Salifert result was 0.5 - 0.6 DKH higher.
My initial reaction is to give more credibility to the Lamotte and Red Sea results partly due to the fact I had sent my water in for testing a while back and the result was lower by a similar amount compared to my Salifert test.
Nevertheless, there is that few drop difference between the end and beyond endpoint for the Red Sea and Lamotte tests. That could make up the difference between them and the Salifert results.
So what I intend to do, next Sunday, is add the reagents for the Red Sea and Lamotte kits until they "fully" reach the beyond endpoint coloration and use the measurement for the previous drop as my final result and compare to my Salifert result

 

[NY_Caveman]

Nice work!

 

[Scrubber_steve]

First the Red Sea - The previous test had a color change that was difficult to nail down. However, the current test has a clear color change from blue/green to green.

I will say that the redsea alk test new version is awesome.
Top Mark's to redsea for listening to us, all.

Same goes for their PO4 test.

 

[Dan_P]

Greetings All,
About a year ago I did an evaluation of Red Sea and Salifert Alkalinity Test kits.
Since that time there have been certain changes made to both kits, so I felt a reevaluation would be in order.
I am also including the Lamotte test kit. It's touted as being extremely accurate and, not surprisingly, more expensive than other test kits.
I should point out that all test kits were purchased within the last 3 month's and have expiration dates that exceed 2 years.
So what is different?
First the Red Sea - The previous test had a color change that was difficult to nail down. However, the current test has a clear color change from blue/green to green. The initial change can be subtle, but is noticeable.
There is also a yellow color which indicates going beyond the endpoint.
As for the Salifert - The endpoint was achieved by sort of a lavender coloration. The current kit has a photo of the endpoint and it is clearly pink.
Similar to the Red Sea test, the Lamotte has an endpoint color of deep purple and a past endpoint color of pink.
So for the last few weeks I have taken a total of three tests for all 3 kits.
Before I discuss my findings, I should explain how I determined the final result for each of the 3 tests.
Salifert - Observed the first sign of pink (light shade) and used that as my endpoint.
Red Sea - Used first appearance of green (absence of blue) although green color might persist for a few drops before turning yellow.
Similarly, there is somewhat of an overlap between the deep purple and pink coloration for the Lamotte test.
For the purpose of the test, I used the 1st drop where pink was noticed - although after shaking the sample the color would revert to the deep purple endpoint. Similar to the Red Sea test, this could persist for a few drops before turning completely pink.

Final Results
In all 3 testings the results from the Lamotte and Red Sea test kits were virtually identical.
In each case the Salifert result was 0.5 - 0.6 DKH higher.
My initial reaction is to give more credibility to the Lamotte and Red Sea results partly due to the fact I had sent my water in for testing a while back and the result was lower by a similar amount compared to my Salifert test.
Nevertheless, there is that few drop difference between the end and beyond endpoint for the Red Sea and Lamotte tests. That could make up the difference between them and the Salifert results.
So what I intend to do, next Sunday, is add the reagents for the Red Sea and Lamotte kits until they "fully" reach the beyond endpoint coloration and use the measurement for the previous drop as my final result and compare to my Salifert result

Thanks for this study report. Very useful. The vivid description of the color changes will help in future purchasing decisions. Looking forwards to next Sunday’s results.

 

[infinite0180]

I was using the new RS alk test for awhile and wound up getting the hanna checker for alk. Sometimes i still go back and use the RS kit because i liked it alot. It was super easy to titrate and i can do it just as fast as i can do the hanna checker... especially when i have a good idea of where my alk should be already!

 

[David S]

I was using the new RS alk test for awhile and wound up getting the hanna checker for alk. Sometimes i still go back and use the RS kit because i liked it alot. It was super easy to titrate and i can do it just as fast as i can do the hanna checker... especially when i have a good idea of where my alk should be already!

I've used the Hanna kits (ALK + P04) but discontinued.
For me they were inconsistent and there was no way (unless you want to return it to Hanna) of calibrating them.
Test kits may not be accurate, but, at the very least, they are consistent. So if you have an idea of the value of the particular parameter you're checking you can adjust the results of your test kit, accordingly.

 

[Oldreefer44]

I had used RS for about a year but decided to try Hanna out because I was adding a doser and wanted to make sure my results were accurate. Found that Hanna was giving me a result of 5.8 DKH versus RS showing 8.1. So I ordered a Salifert and it also showed a reading of 8.1 DKH. So decided to get ahold of Hanna to see what gives and also order an ICP test. Surprisingly my ICP result showed a KH of 5.8 DKH. Guess I'm sticking with Hanna while .

 

[Scrubber_steve]

I had used RS for about a year but decided to try Hanna out because I was adding a doser and wanted to make sure my results were accurate. Found that Hanna was giving me a result of 5.8 DKH versus RS showing 8.1. So I ordered a Salifert and it also showed a reading of 8.1 DKH. So decided to get ahold of Hanna to see what gives and also order an ICP test. Surprisingly my ICP result showed a KH of 5.8 DKH. Guess I'm sticking with Hanna while .

I checked my new version RS alk against NSW. Pleasantly surprised to see how accurate it was

 

[JimWelsh]

I had used RS for about a year but decided to try Hanna out because I was adding a doser and wanted to make sure my results were accurate. Found that Hanna was giving me a result of 5.8 DKH versus RS showing 8.1. So I ordered a Salifert and it also showed a reading of 8.1 DKH. So decided to get ahold of Hanna to see what gives and also order an ICP test. Surprisingly my ICP result showed a KH of 5.8 DKH. Guess I'm sticking with Hanna while .

Alkalinity cannot be measured by ICP.

 

[David S]

I had used RS for about a year but decided to try Hanna out because I was adding a doser and wanted to make sure my results were accurate. Found that Hanna was giving me a result of 5.8 DKH versus RS showing 8.1. So I ordered a Salifert and it also showed a reading of 8.1 DKH. So decided to get ahold of Hanna to see what gives and also order an ICP test. Surprisingly my ICP result showed a KH of 5.8 DKH. Guess I'm sticking with Hanna while .

My ICP test also showed low ALK versus my test kits, but that also included the Hanna.
Go figure

 

[David S]

OK so as promised I did another test today.
The reason I waited a week before retesting was primarily due to the expense of the Lamotte kit.
The Red Sea and Salifert kits are relatively inexpensive so I did two additional tests for them during the week.
In both tests the Salifert reading was 0.7 DKH higher than the Red Sea result.
I did notice that no more 2 drops (sometimes 1 sometimes 2) separated the green end color and yellow "overdose" color on the Red Sea test. So kudos to them for developing a test that gives definitive color results.
As far as today's results; Red Sea was 7.15 DKH, Salifert was 7.85 DKH and Lamotte was 7.39 DKH.
I must say that I had an initial result of 6.6 DKH with the Lamotte. I redid the test, this time shaking a bit more after adding the tablet to the test water and shaking the Titrant prior to adding it to the sample.
The results for the Lamotte and Red Sea are very close.
Adding one more drop to the Red Sea test would have resulted in a DKH of 7.3. The coloration had only a faint yellowish color which could have been interpreted as the end color.
In the final analysis all 3 kits are very consistent.
Red Sea and Lamotte provide similar results while Salifert is 0.5 to 0.7 DKH higher.
I should also mention that I had 2 separate Salifert kits, both of which were well within their expiration period. I got the same result, regardless of which kit I used.
I personally think the true ALK of my tank is reflected in either the Red Sea or Lamotte tests, however as the Salifert results are consistently higher by a similar margin they can be used as well.

 

[JimWelsh]

Sounds to me like you're overshooting the endpoint on the Salifert kit by taking it to pink instead of the aforementioned lavender.

 

[Dan_P]

OK so as promised I did another test today.
The reason I waited a week before retesting was primarily due to the expense of the Lamotte kit.
The Red Sea and Salifert kits are relatively inexpensive so I did two additional tests for them during the week.
In both tests the Salifert reading was 0.7 DKH higher than the Red Sea result.
I did notice that no more 2 drops (sometimes 1 sometimes 2) separated the green end color and yellow "overdose" color on the Red Sea test. So kudos to them for developing a test that gives definitive color results.
As far as today's results; Red Sea was 7.15 DKH, Salifert was 7.85 DKH and Lamotte was 7.39 DKH.
I must say that I had an initial result of 6.6 DKH with the Lamotte. I redid the test, this time shaking a bit more after adding the tablet to the test water and shaking the Titrant prior to adding it to the sample.
The results for the Lamotte and Red Sea are very close.
Adding one more drop to the Red Sea test would have resulted in a DKH of 7.3. The coloration had only a faint yellowish color which could have been interpreted as the end color.
In the final analysis all 3 kits are very consistent.
Red Sea and Lamotte provide similar results while Salifert is 0.5 to 0.7 DKH higher.
I should also mention that I had 2 separate Salifert kits, both of which were well within their expiration period. I got the same result, regardless of which kit I used.
I personally think the true ALK of my tank is reflected in either the Red Sea or Lamotte tests, however as the Salifert results are consistently higher by a similar margin they can be used as well.

One thing that you can do to sneak up closer to the endpoint is to use half drops, i.e., forming a small drop of titrant too small to fall off the syringe tip. By touching this mini drop to the side of the test vessel just above the test solution, and then swirling the solution to wash the drop off the wall. Using this approach could get these results closer yet. Of course, this assumes you are titrating with a syringe I converted the API alkalinity test (inexpensive test kit) which is a drop from a bottle method to a syringe titration method.

Thanks again for the study.

 

[David S]

One thing that you can do to sneak up closer to the endpoint is to use half drops, i.e., forming a small drop of titrant too small to fall off the syringe tip. By touching this mini drop to the side of the test vessel just above the test solution, and then swirling the solution to wash the drop off the wall. Using this approach could get these results closer yet. Of course, this assumes you are titrating with a syringe I converted the API alkalinity test (inexpensive test kit) which is a drop from a bottle method to a syringe titration method.

Thanks again for the study.

Actually that is exactly what I do.

 

[David S]

Sounds to me like you're overshooting the endpoint on the Salifert kit by taking it to pink instead of the aforementioned lavender.

Jim
I can use the lavender results which would bring the Alkalinity result lower, but probably not by much as I am using a very light pink result.
As mentioned, Salifert's current kit shows a photo of the end result and it is a rather clearly defined pink color. You'd think they know what the end result should look like.
I will test using the lavender color later today and report the results.

 

[Randy Holmes-Farley]

Jim
I can use the lavender results which would bring the Alkalinity result lower, but probably not by much as I am using a very light pink result.
As mentioned, Salifert's current kit shows a photo of the end result and it is a rather clearly defined pink color. You'd think they know what the end result should look like.
I will test using the lavender color later today and report the results.

There are only two things that matter in an alkalinity test (aside from minor points like the salinity and the actual starting alkalinity):

1. The concentration of the acid added in the titration.
2. The pH of the point where you call the titration done.

So in the vein of "You'd think they know what the end result should look like.", they should also know the concentration of the acid they use, and the color of their dyes used at the true endpoint.

If the result you are getting is not accurate at the exact color they show, one of these simple things must be off.

 

[JimWelsh]

FWIW, the pH 4.5 Buffer Powder Pillows referenced in this post are made specifically to check the endpoint color of an alkalinity titration: DIY Alk test discussion thread

 

[David S]

FWIW
Did a test earlier this morning using the Red Sea and Salifert kits.
I used the Lavender coloration (the drop just prior to the sample showing a hint of pink color). The DKH still exceeded the Red Sea result by 0.3+ DKH.
My gut feeling is that while the Salifert kit gives very consistent results, the numbers run high.
I am not just basing it on the fact that the Lamotte and Red Sea tests give lower (and similar) results compared to the Salifert but more so based on the Alkalinity results that I got when I did an ICP test with ATI, one year ago.
They also test for Carbonate in DKH and I noticed that their result was almost 1 DKH lower than my result.
At the time, I was only using the Salifert test.
I hadn't started using the Lamotte test yet and while I had a Red Sea kit, it was the older version (orange end point) which I had no confidence in and didn't bother to use.
I was so confident in the Salifert result that I questioned ATI about their result.
As they did not have any remnants of my original sample, they offered to run the ALK test twice when I submit my next sample.
Have not done any ICP tests recently, but the next time I do I'll consider ATI so I can compare my 3 test kits with their results.
So my question is; has anyone tested with ATI, who also use a Salifert kit, and if so were there similar discrepancies?

 

[David S]

Alkalinity cannot be measured by ICP.

Jim
Didn't mean to suggest the Alkalinity was tested using the ICP process, merely that it is included as part of ATI's overall procedure.

 

[Randy Holmes-Farley]

FWIW
Did a test earlier this morning using the Red Sea and Salifert kits.
I used the Lavender coloration (the drop just prior to the sample showing a hint of pink color). The DKH still exceeded the Red Sea result by 0.3+ DKH.
My gut feeling is that while the Salifert kit gives very consistent results, the numbers run high.
I am not just basing it on the fact that the Lamotte and Red Sea tests give lower (and similar) results compared to the Salifert but more so based on the Alkalinity results that I got when I did an ICP test with ATI, one year ago.
They also test for Carbonate in DKH and I noticed that their result was almost 1 DKH lower than my result.
At the time, I was only using the Salifert test.
I hadn't started using the Lamotte test yet and while I had a Red Sea kit, it was the older version (orange end point) which I had no confidence in and didn't bother to use.
I was so confident in the Salifert result that I questioned ATI about their result.
As they did not have any remnants of my original sample, they offered to run the ALK test twice when I submit my next sample.
Have not done any ICP tests recently, but the next time I do I'll consider ATI so I can compare my 3 test kits with their results.
So my question is; has anyone tested with ATI, who also use a Salifert kit, and if so were there similar discrepancies?

What do you mean they also test for carbonate?

Why would there be a relationship between ATI results and Salifert?