Alk test not reliable - hanna checker

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lost66

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My newest addition to my reef is calcium reactor and I had some difficulties to set it up correctly so I was testing water daily for a month or so. I was able to keep something around 9.0 alk. When I was approaching 50% of the reagent of hanna checker I noticed that alk started to raise. I thought maybe corals started to die and they don't consume that much anymore so I was reducing drops from calcium reactor. But even then it started to raise by around 0.1 daily. When I was almost done with reagent the last sample showed me 11.3 and I tested the water one more time using brand new bottle. And I was shocked how different result was. It showed me 8.9. What the heck? Both bottles have plenty of live time, I keep all reagents in the same environment.

Do you guys have similar experience? How to approach stability when I have such drop between reagent change?
 
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Jason Arego

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Has always happened to me when the reagent starts getting low. I avoid this by buying 2 sets of reagent at a time and if I suspect a test I'll use the other reagent to confirm. I think it's due to cleaning the pipette and if it's not completely dry everytime it will over time degrade the reagent so when it's near the bottom the contamination eventually spirals the results out of control. This is my best guess as to why and doing my own tests to try to nail down why it happens.
 

T-J

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I always shake my reagent bottle before drawing it out for testing. Not sure if it settles/separates, but I always figured it can't hurt. I've never noticed any difference in my results based on how much reagent is left in the bottle.

I'd suggest you take a water sample to a LFS and have them check it. Or, you can buy another Alk test kit to verify. I always have kits around to verify my Hannah results if they seem off.
 

SweetReefOH

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I’ve been using the Hanna alk checker for years. I’ve never had a “drifting upward” experience toward the end of the bottle. There must be a flaw in how you’re testing that is contaminating, concentrating or diluting the reagent over time.

The one annoying observation I did learn over time is that the alk can be drastically off from one reagent lot to a different reagent lot. I’ve experienced them being off as much as .6 DKH. That doesn’t sound like a lot but when you’re dealing with expensive acros, alk stability is extremely important. Hence, I went to the Trident and only occasionally use my alk checker to confirm my Trident results.

This is just my humble opinion and observations.
 

homer1475

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Only notice when I have about 1 to 2 tests left…some folks count how many tests they do and when they get close to the limit they open a new reagent bottle no matter how much is left
I do this exact thing. There is 25 tests in a bottle, but 30ml of reagent. When I started marking the bottles and only using 25 tests, each bottle was much more consistent.

@Hanna Instruments has stated this many times. But they are also known for having bad batches of reagents in the past too.
 

homer1475

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Also if you leave the bottle open for any amount of time(even the amount of time it takes to run the test), after a while it will develop "crusties" or "floaties"(for the lack of a better term?). That will also throw the test off.

It's best practice to just open bottle, draw up reagent, immediately tightly recap the bottle.

I often hear people mention cleaning the syringe for the reagent, but I never have. I simply just depress the plunger into the vial completely, and throw it back in the box.
 
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lost66

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after a while it will develop "crusties" or "floaties"(for the lack of a better term?). That will also throw the test off.
This is exactly what happens in my case too. I always shake the bottle before I take the liquid and I notice the further with test I am in that bottle, the more gunk is in the sample. I never leave reagent open for more than few seconds. After testing I flush that plastic tip with RODI water and blow the rest of the water off.

I think I will start to collect these plastic ends and don't blow them off and just leave them for few days to dry and use dry one for testing.

I am glad I am not the only one with this issue.

@SweetReefOH I really wonder what do you do that you have never had an issue with those tests. Can you please shed some light what is your procedure?
 

FishyFishFish

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I'm about to trash mine!

Maybe not just yet, but I can't get reliably consistent results. I tested yesterday at 7 dkh. I added baking soda that should have raised it to 7.5. I immediately retested, with the same reagent, and it showed 8.5.

I tested again tonight, with new reagent, and it shows 7 again, which I don't believe.

I am very careful with cleaning and I always wipe the vials and place them in the tester in the same orientation.

I am going to buy a Salifert kit to cross check the results.
 

temple2101

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Glad I came across this thread as I’ve been wondering about these issues myself. The biggest thing I’ve noticed is inconsistencies from one bottle to the next. At first I thought it was coincidence, but now that I’ve gone through a number of reagents I’ve decided it’s rare that a new bottle gives the same results as the old. I’ve tried not to worry too much and just ensure my readings stay consistent within the same bottle. Would be great to have a bit more confidence in the number though.
 
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Crustaceon

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Hanna can be hit-and-miss on their reagents, which really sucks when their meters are supposed to get you better accuracy over titration tests. I’ve debated going back to salifert tests just for the sake of cost and having results that might not be perfect, but will at least be consistently close to the mark. But for phosphate...yeah, hanna is the only option.
 

SweetReefOH

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This is exactly what happens in my case too. I always shake the bottle before I take the liquid and I notice the further with test I am in that bottle, the more gunk is in the sample. I never leave reagent open for more than few seconds. After testing I flush that plastic tip with RODI water and blow the rest of the water off.

I think I will start to collect these plastic ends and don't blow them off and just leave them for few days to dry and use dry one for testing.

I am glad I am not the only one with this issue.

@SweetReefOH I really wonder what do you do that you have never had an issue with those tests. Can you please shed some light what is your procedure?
Without watching you do your test, I can only speculate.

The main thing I focus on is consistency. First, I always tested at 4pm every single day. Second, When I fill the test vial with tank water, I purposely tilt the vial back and forth to get the big U shaped curve in my water line and then I will add a drop of tank water at a time until the mid point of that curve is barely touching the line. Then I cap it, blow on it to get the outside of the vial fogged up and then I clean the outside of the vial with my shirt. As others have mentioned, I always orient the vial in the tester with the “10mL” mark facing toward me. Push the button. As that is doing its thing, I will pull the reagent up in the syringe, set it aside, close the reagent bottle. So, the reagent is only open about 10 seconds. At that point the test is ready and I pull out the vial and add the reagent. NEVER letting the syringe touch the saltwater! Cap it, then tilt the vial back and forth exactly 5 times. I will blow on the vial again to fog it up and then clean the outside of the vial with my shirt, again. This is to remove any fingerprints from handling the vial to add the reagent. Add it to the checker by only holding onto the cap.

I am a numbers freak and I’m obsessed with consistency. So what I’ve noticed over the years is that debris in the test vial, fingerprints, etc. ALL will effect your consistency with readings. If you’re squirting the reagent into the vial too fast and with enough force that the saltwater is splashing back up onto the syringe, then you contaminate the reagent bottle the next time you pull reagent.

If you want to test your process for consistency. Get 3 test vials and run the tests back to back with each vial. The numbers should be exactly the same. If they are not, you’re not consistent with something in the process. If you want to test your checkers accuracy, get 2 test vials. 1 with saltwater only and one with saltwater+reagent. Run multiple tests back to back. If the number is not consistently the same, your Hanna my be defective.

These are my habits, I hope it helps you guys find some consistency with your tests!
 

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That is almost exactly what I do (except I use the Hanna cleaning cloths and not my shirt ;) ). However, the results are still inconsistent to the point that I no longer trust them.

The only thing I am going to pay even more attention to than I was already, is to make sure that the reagent syringes and tips are 100% dry (I clean them with RODI water after every use). I'm fairly sure that they have been dry so far, but this is the only thing left that I can think of (other than a colorimiter or reagent error) that could be causing my problems.
 
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lost66

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@SweetReefOH Thanks for description. I do it more or less the same beside touching the saltwater when injecting reagent to the vial. I will work on that. I wonder how do you clean syringe and that plastic tip? How do you dry it?

@FishyFishFish same here, I think I contaminate the reagent somehow by syringe.
 
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SweetReefOH

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@SweetReefOH Thanks for description. I do it more or less the same beside touching the saltwater when injecting reagent to the vial. I will work on that. I wonder how do you clean syringe and that plastic tip? How do you dry it?

@FishyFishFish same here, I think I contaminate the reagent somehow by syringe.
Honestly, I don’t clean the reagent syringe at all. I keep the kit case open and just lay the syringe in it when I’m done.
 

Uncle99

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I test Alk, once a week, every week, with my Hanna checker and never had a problem four years now. Love it.
What do notice on both Alk and Phosphorus checkers is if C1 flashes unusually long, the reading, when completed, is zero.
Rare but consistent.
 

Saaqib_Ansari

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Towards end of the reagent my results went from 8.5 to 6 began dosing until the the last test showed 8 got a new reagent tested few days later and apparently it was 11.8!! Checked in w Red Sea test kit and it was roughly 11.5 too. I think best bet is if the results look off double check with another test kit
 

Reef.

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Aqua forest is a good option, it comes with a small bottle of calibration solution so you know the colour you are aiming for, I have Salifert too and they both read exactly the same (the stopping point for Salifert being a lavender colour not pink).
 
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