Alk testing discrepancy

[ssster2020]

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?

 

[T-J]

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.

 

[ssster2020]

Thanks I checked the reagent level and it is maybe 1/2 full, so it should be OK. Maybe I'll order a new bottle anyway as a way to rule the reagent out of the diagnosis. The good news is I had about 6 weeks of smooth sailing which is a record for me! lol

 

[mdb_talon]

My bet is the hanna is the one that is off. I posted so many times about my experience with it people probably tired of hearing the details, but I found it to be very innacurate (in my case it was a huge difference between regeant lot #s).

 

[Reef.]

Thanks I checked the reagent level and it is maybe 1/2 full, so it should be OK. Maybe I'll order a new bottle anyway as a way to rule the reagent out of the diagnosis. The good news is I had about 6 weeks of smooth sailing which is a record for me! lol

try testing your salt mix, if you trust the brand you use to have a somewhat accurate alk lvl in their salt, see if your Hanna tests that correctly.

Chances are it’s a testing error, leaving lid of the Hanna reagent bottle for a little too long can do it, or a salinity issue, very easy to get your salinity wrong, that would then throw your other parameters off.

 

[mdb_talon]

try testing your salt mix, if you trust the brand you use to have a somewhat accurate alk lvl in their salt, see if your Hanna tests that correctly.

Chances are it’s a testing error, leaving lid of the Hanna reagent bottle for a little too long can do it, or a salinity issue, very easy to get your salinity wrong, that would then throw your other parameters

Could be testing error yes, but salinity issues would presumably throw off both tests not just one.

 

[ssster2020]

That is my thought, too. I started to use it because I was getting tired of trying to figure out when the red sea went from blue to green! And it seemed to work initially but now I'm stumped

try testing your salt mix, if you trust the brand you use to have a somewhat accurate alk lvl in their salt, see if your Hanna tests that correctly.

Chances are it’s a testing error, leaving lid of the Hanna reagent bottle for a little too long can do it, or a salinity issue, very easy to get your salinity wrong, that would then throw your other parameters off.

 

[ssster2020]

My plan is to lower my dosing rate, continue testing daily, and order a different test kit. Any suggestions for the test kit?

try testing your salt mix, if you trust the brand you use to have a somewhat accurate alk lvl in their salt, see if your Hanna tests that correctly.

Chances are it’s a testing error, leaving lid of the Hanna reagent bottle for a little too long can do it, or a salinity issue, very easy to get your salinity wrong, that would then throw your other parameters off.

I will test the salt mix, good idea, it should at least give me a standard.

 

[Pistondog]

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?

I had the same problem with Hanna alk tester. Dropping over a week, me increasing triton dose. After 2 weeks I tested with Red Sea and got 11 dkh, vs 8 target.
Hanna was stupid low, like 6. Bought new Hanna, tested old unit with new reagent, same 6 dkh. New one matched rs.
It happens.

 

[ssster2020]

try testing your salt mix, if you trust the brand you use to have a somewhat accurate alk lvl in their salt, see if your Hanna tests that correctly.

Chances are it’s a testing error, leaving lid of the Hanna reagent bottle for a little too long can do it, or a salinity issue, very easy to get your salinity wrong, that would then throw your other parameters off.

TBH I have trust issues with my major parameters. I check salinity using the hanna checker and a refractometer. Both of which were calibrated last week so salinity should be accurate, 1.025 specific gravity.

 

[mdb_talon]

My plan is to lower my dosing rate, continue testing daily, and order a different test kit. Any suggestions for the test kit?

I will test the salt mix, good idea, it should at least give me a standard.

I recommend both salifert and elos for alkalinity. Never have any issues. I would use api before i trusted the hanna though.

Careful with using salt mix as baseline. There is some variation anyway even if you do get it properly mixed.

 

[ssster2020]

I had the same problem with Hanna alk tester. Dropping over a week, me increasing triton dose. After 2 weeks I tested with Red Sea and got 11 dkh, vs 8 target.
Hanna was stupid low, like 6. Bought new Hanna, tested old unit with new reagent, same 6 dkh. New one matched rs.
It happens.

Perfect thanks for the experience. I'm still new at this and every time something different happens I kind of panic and really rely on experienced reefers to calm me down and give me direction.

 

[Pistondog]

Recently had problems with their low range nitrate tester. The vial would not c2, was low or high. Watched the green led inside and it was dim/fading. Replaced with high range nitrate tester, which is much more user friendly.
Hobby grade stuff.

 

[ssster2020]

I recommend both salifert and elos for alkalinity. Never have any issues. I would use api before i trusted the hanna though.

Careful with using salt mix as baseline. There is some variation anyway even if you do get it properly mixed.

I bought the Hanna Alk tester basically like I said I was having trouble differentiating the colour change on my Red Sea. But also I was having trouble with measuring phosphates with the checker I was using so I bought the hanna phosphate checker, it was life changing to me I love it. I think I'll simply go back to manual testing for alk

 

[X-37B]

I have been using the Hanna alk tester, same one, for over 5 years.
I also use salifert and elos as a cross reference. 95+% of the time the hanna is right on. I have the standards too.
For the last few bottles, I check alk every morning, the Hanna has been reading .5 lower than both salifert and elos.
I have never had the alk be off more than that. If it was it was always operator error.
Just my experience.

 

[Reef.]

Could be testing error yes, but salinity issues would presumably throw off both tests not just one.

the OP said they only tested with the second test kit the Red Sea when they saw the alk drop, so the Red Sea wouldn’t have changed result, the Hanna also showed a stable result after the initial drop, so yes it could be a salinity issue, worthwhile to at least check.

 

[mdb_talon]

the OP said they only tested with the second test kit the Red Sea when they saw the alk drop, so the Red Sea wouldn’t have changed result, the Hanna also showed a stable result after the initial drop, so yes it could be a salinity issue, worthwhile to at least check.

Hanna showed 6.9. Red Sea showed 9. The difference between the two test cannot be explained by a salinity issue.

 

[Reef.]

Hanna showed 6.9. Red Sea showed 9. The difference between the two test cannot be explained by a salinity issue.

I never said it could!

I said the drop the OP saw could have been because of a salinity issue.

 

[mdb_talon]

I never said it could!

I said the drop the OP saw could have been because of a salinity issue.

Ya I guess so. One that only impacts hanna tester and does not impact the calc test at all.

 

[Reef.]

Ya I guess so. One that only impacts hanna tester and does not impact the calc test at all.

with the other tests being so dependent on stopping at the same point each time, I wasn’t giving the OP’s results with those too much weight.