Alk testing discrepancy

[CapeCoralDan]

I apologize if there is already a thread that is discussing this. I couldn't find a specific one.

I test my tank major parameters weekly, Wednesday afternoon, and do an approximate 10% water change Saturday morning.
Last week my Alk test, I've been using a Hanna checker for 6 weeks, had dropped to 7.8 from the mid 8's where it's been for months. I increased my dosing rate to make it up. This week it was 6.9? So I got out my old Red Sea manual test kit, it showed 9. Incidentally the Ca level both weeks was 460 where it's been consistently. The Mg level was at 1250 both weeks. And my PH is and has been consistently 8.4, daily swing from 8.35 to 8.45.

I retested Alk using both methods, the results were 6.8 on Hanna and 9 using Red Sea.

I then checked the doser, made sure the lines weren't plugged, calibration was marginally low but not bad, so I think I can rule it out as a problem.

I don't have a tie breaking test kit and really don't have access to one quickly.

Does anyone have any ideas? Is there any history of hanna Alk checker problems?

My Hanna is always 2 points low. Really wish it worked, so much easier.

 

[Reef.]

My Hanna is always 2 points low. Really wish it worked, so much easier.

Keep going to buy one then see posts like this!

 

[Rmckoy]

Any chance you're near the end of the reagent bottle with the Hanna checker? I've read that some people experience testing issues when they are near the end of the bottle.
I've never had such a discrepancy with my Hanna checker.

Always shake the bottle prior to testing .
this way when you get close to the bottom , it gives the same test results .
I have had issues where the end of the bottle was off .
Could There be something in the bottle that settles .
Causing the 1ml of reagent to be different concentration ?

 

[mdb_talon]

Always shake the bottle prior to testing .
this way when you get close to the bottom , it gives the same test results .
I have had issues where the end of the bottle was off .
Could There be something in the bottle that settles .
Causing the 1ml of reagent to be different concentration ?

Presumably there could be. I will say though that I did test using 3 different regeant bottles from three different lot numbers. One was near empty, but the other two were full (none were expired at the time). I had a very large difference (over 2dkh) between my "old" bottle and the brand new bottle. Was able to consistently get that difference depending which bottle I used. Then ordered another new bottle and it was between the two readings of the other bottles (about .8 lower than the first new bottle). Again I could consistently get the same results over and over with each regeant bottle so it was not testing error.

Only good thing about it is saltwateraquarium.com was kind enough to refund me for both bottles and did not make me go through aggravation of returning them.

 

[ssster2020]

Always shake the bottle prior to testing .
this way when you get close to the bottom , it gives the same test results .
I have had issues where the end of the bottle was off .
Could There be something in the bottle that settles .
Causing the 1ml of reagent to be different concentration ?

Yep, and I don't shake the bottle tomorrow I'll sample again and shake it, I believe the hanna was accurate until the last 2 weeks. now IDK

 

[ssster2020]

I fully accept that it could be operator error. But the second time I don't think so, I was super careful. I even switched the cuvettes and the result was virtually identical. I think I'm believing the theory about the reagent. My big problem is my LFS is not very local so it's hard to simply drop in and pick up a new bottle. But I'll order some new reagent and maybe a different test kit online. It's only money lol, and I've spent more in this hobby on dumber things.

 

[Rmckoy]

I fully accept that it could be operator error. But the second time I don't think so, I was super careful. I even switched the cuvettes and the result was virtually identical. I think I'm believing the theory about the reagent. My big problem is my LFS is not very local so it's hard to simply drop in and pick up a new bottle. But I'll order some new reagent and maybe a different test kit online. It's only money lol, and I've spent more in this hobby on dumber things.

This hobby seams to be all about buying something else

my lfs has shipping .. I go online , order and a few days later it’s delivered

I hate driving 1.5 hours to the closest lfs

 

[ssster2020]

Isn't it though,I thought it was only me! I'm the same as you except he's 3 hours away, more these days because of major road construction and doesn't ship. I do get deliveries from another source who are really good IMO. Service is quite quick considering the postal service.

 

[Neil Cohen]

Really disappointed in the Hanna checkers. I bought them because I couldn’t trust my eyes and opinion. A colorimeter doesn’t have opinions. Should be a way to calibrate the results, not just zero it out. If it always reads 1 point lower, you adjust in your head. But with a doser, you can “fix” the amounts. Should be the same here. If a proven reference sample has a dkh of 9, then you should be able to change the meter.

which would be a money maker for them, just like the reference saltwater they sell for their digital salinity meter. Not that you can’t create reference material but what to check it on would the challenge. I would pay for lab verified samples to know the deviation of my tester.

Does that exist?

 

[X-37B]

Really disappointed in the Hanna checkers. I bought them because I couldn’t trust my eyes and opinion. A colorimeter doesn’t have opinions. Should be a way to calibrate the results, not just zero it out. If it always reads 1 point lower, you adjust in your head. But with a doser, you can “fix” the amounts. Should be the same here. If a proven reference sample has a dkh of 9, then you should be able to change the meter.

which would be a money maker for them, just like the reference saltwater they sell for their digital salinity meter. Not that you can’t create reference material but what to check it on would the challenge. I would pay for lab verified samples to know the deviation of my tester.

Does that exist?

Randy has a way to make a standard. I have it saved somewhere just forgot about it.
I am going to locate it and start using it.

 

[ssster2020]

Really disappointed in the Hanna checkers. I bought them because I couldn’t trust my eyes and opinion. A colorimeter doesn’t have opinions. Should be a way to calibrate the results, not just zero it out. If it always reads 1 point lower, you adjust in your head. But with a doser, you can “fix” the amounts. Should be the same here. If a proven reference sample has a dkh of 9, then you should be able to change the meter.

which would be a money maker for them, just like the reference saltwater they sell for their digital salinity meter. Not that you can’t create reference material but what to check it on would the challenge. I would pay for lab verified samples to know the deviation of my tester.

Does that exist?

I’m expecting new reagent and a set of (standard?) calibration fluid in the mail today. I’ll be curious as to what the samples show.

 

[X-37B]

I’m expecting new reagent and a set of (standard?) calibration fluid in the mail today. I’ll be curious as to what the samples show.

I have the standards but they are not the same as Randys. Mine read in range but are still off 0.5.
The one Randy has makes a solution at a specific alk. I will go look for it now.

 

[X-37B]

Here it is.

DIY alkalinity standard

For folks who may want to evaluate the accuracy of their alkalinity test kits, here are two suggested ways to do it. One is DIY and one is a mostly commercial standard with one DIY step. Method 1 Standard solutions could be made with sodium bicarbonate, but it can be hard to be sure it hasn't...

www.reef2reef.com

 

[Timfish]

FWIW I always have multiple alklinity test kits and periodicly check them against each other in case reagents start to go south. I wasn't impressed with Hanna's alkalinity tester when I got one. I checked it against a friends kit and using the reagents from both testers in each with the same sample of water I got 4 results that differed by almost 1 dKH

 

[ssster2020]

So I received the "standard" solutions. The standard KH should produce a rest result of 4.9 + or - .3 dKH according to the documentation. When I tested it the result is 4.3 dKH. If the +- .3 is used it could be as low as 4.0 or as high as 4.6. Either way not good. I think the checker is too expensive to be this inaccurate especially since there is no facility to calibrate it.
Not sure where to go from here.
I agree with Timfish, really multiple tests are required to confirm results.

 

[ssster2020]

So, I know this whole topic is getting boring, it's important to me to get my ALK to the level I want it, somewhere around 8. I have a coral that I've been told is suffering from burnt tips due to ALK swings or higher ALK level than it wants so I want to get this corrected.
I tested the hanna checker with the standard solutions and my checker failed as I have already documented in this thread.
I went ahead and retested my tank ALK level and got the following results:
Red Sea kit 9 dKH, basically where it's indicated the last week
Hanna with old reagent 6.9 dKH
Hanna with new reagent 8.6 dKH

So, I'm not 100% sure it is safe for me to do this, but if I add .5, the error in my checker when testing the standard, to the "new reagent" result it matches the red sea result.

Does that make sense? I am going to my LFS next week so maybe I'll pick up another brand of ALK test kit. I believe that the RED Sea kit has been accurate but I can't sleep without confirming it.

But I suck at identifying the colour change to green as I said earlier.

 

[mdb_talon]

So, I know this whole topic is getting boring, it's important to me to get my ALK to the level I want it, somewhere around 8. I have a coral that I've been told is suffering from burnt tips due to ALK swings or higher ALK level than it wants so I want to get this corrected.
I tested the hanna checker with the standard solutions and my checker failed as I have already documented in this thread.
I went ahead and retested my tank ALK level and got the following results:
Red Sea kit 9 dKH, basically where it's indicated the last week
Hanna with old reagent 6.9 dKH
Hanna with new reagent 8.6 dKH

So, I'm not 100% sure it is safe for me to do this, but if I add .5, the error in my checker when testing the standard, to the "new reagent" result it matches the red sea result.

Does that make sense? I am going to my LFS next week so maybe I'll pick up another brand of ALK test kit. I believe that the RED Sea kit has been accurate but I can't sleep without confirming it.

But I suck at identifying the colour change to green as I said earlier.

I dont know about red sea, but I find the color change with Salifert and Elos extremely simple to see. Sure it is not as precise as using a digital meter. Might have a drop and it changes just partially between a color, but in my opinion gives a very good idea of what the value is within .5dkh. To me that is more valuable than having a very precise number that may be 2dkh+ off. I am sure you can get bad regents with other brands also, but personally in decades of testing alk I have never had it happen to an obvious extent like I did with hanna (in my case testing three different reagent batches).

As for adding .5 to the hanna result to make it match what you believe is the correct number I dont know, but I will say in my case with all the bad reagents they were consistent and was able to get repeatable results which made me think I could probably just apply an "adjustment factor" to each result. However not sure if when the alk significantly changes whether the margin of error changes or remains the same which is why I did not even end up using my bottles. Hopefully that makes sense?

 

[ssster2020]

I dont know about red sea, but I find the color change with Salifert and Elos extremely simple to see. Sure it is not as precise as using a digital meter. Might have a drop and it changes just partially between a color, but in my opinion gives a very good idea of what the value is within .5dkh. To me that is more valuable than having a very precise number that may be 2dkh+ off. I am sure you can get bad regents with other brands also, but personally in decades of testing alk I have never had it happen to an obvious extent like I did with hanna (in my case testing three different reagent batches).

As for adding .5 to the hanna result to make it match what you believe is the correct number I dont know, but I will say in my case with all the bad reagents they were consistent and was able to get repeatable results which made me think I could probably just apply an "adjustment factor" to each result. However not sure if when the alk significantly changes whether the margin of error changes or remains the same which is why I did not even end up using my bottles. Hopefully that makes sense?

Thanks I went with Salifort, and I agree it is easier to read than Red Sea but it's probably a personal thing. I have put the Hanna away.

 

[Dcloser12]

I have every hanna tester. Low range nitrate is junk. Calcium tester is also junk. I use redsea dor both. The alk tester is touchy. The only sure way I have found is to take c1 pull it at c2, add reagent to c1, test that vial. Like wise take the phosphate tester, do the same. It will show a different result than using 2 separate glasses. Idk if it's contamination inside or outside the vial but I have personally found obscured results using separate containers. I use redsea to verify alk. It's normally spot on within 1dkh

 

[ssster2020]

you know now that you said that, I used to use the same vial but stopped after wasting a few of the testing packets. I wonder if that is when my results started to change?