Hanna DKH Checker incorrect?

[Dakoda]

So, here is my dilemma.

I have been testing my tank religiously with the Hanna DKH Checker for the last 2 years. I do not currently use a Salifert or any other brand DKH checker to validate the test results of the Hanna checker.

I have prepared three 5 gallon buckets of salt water for a 15 gallon water change today. I measured the DKH of my tank at 10.2 DKH and then went to check the DKH of the fresh salt water. This was prepared with the Red Sea Blue Bucket Salt, I checked the ICP analysis of the batch that I received and according to their ICP analysis the DKH of the salt should measure out to 7.868. I did not use RODI water as I was cutting corners today (I know, mistake on my part).

After testing the DKH of each bucket of fresh salt water the results were as follows: first bucket - 11.1 DKH, second bucket 11.3 DKH, third bucket 11.4 DKH. All three results were higher than what the ICP analysis of the bucket batch listed. I ensured that I recalibrated my refractometer and double checked that the salinity of each bucket came out to 1.025. I also used a fresh container of Alk reagent (lot 0159) to see if there was maybe an expired reagent issue, no dice there.

Besides the obvious of going out tomorrow to buy a secondary DKH checker to confirm the accuracy of the Hanna checker, what else can I do here? Is it possible that my tap water is the culprit and elevated the DKH of the water that much from where the bucket of salt said it would mix to? Has anyone else experienced this issue with either the Hanna DKH checker or with the Red Sea Blue Bucket of salt coming out higher than advertised?

Thank you all in advance!

 

[Opus]

You could buy a gallon of distilled water and add salt to it and see what it reads.

 

[Reef.]

That’s like following a bread recipe that calls for milk but instead using orange juice then wondering why it tastes strange!

Yes it’s most likely the tap water…not much of a short cut it seems

 

[gbroadbridge]

So, here is my dilemma.

I have been testing my tank religiously with the Hanna DKH Checker for the last 2 years. I do not currently use a Salifert or any other brand DKH checker to validate the test results of the Hanna checker.

I have prepared three 5 gallon buckets of salt water for a 15 gallon water change today. I measured the DKH of my tank at 10.2 DKH and then went to check the DKH of the fresh salt water. This was prepared with the Red Sea Blue Bucket Salt, I checked the ICP analysis of the batch that I received and according to their ICP analysis the DKH of the salt should measure out to 7.868. I did not use RODI water as I was cutting corners today (I know, mistake on my part).

After testing the DKH of each bucket of fresh salt water the results were as follows: first bucket - 11.1 DKH, second bucket 11.3 DKH, third bucket 11.4 DKH. All three results were higher than what the ICP analysis of the bucket batch listed. I ensured that I recalibrated my refractometer and double checked that the salinity of each bucket came out to 1.025. I also used a fresh container of Alk reagent (lot 0159) to see if there was maybe an expired reagent issue, no dice there.

Besides the obvious of going out tomorrow to buy a secondary DKH checker to confirm the accuracy of the Hanna checker, what else can I do here? Is it possible that my tap water is the culprit and elevated the DKH of the water that much from where the bucket of salt said it would mix to? Has anyone else experienced this issue with either the Hanna DKH checker or with the Red Sea Blue Bucket of salt coming out higher than advertised?

Thank you all in advance!

Are you using tap water or RODI filtered water?

If using tap water all bets are off. The salt mixes assume you are starting with RODI.

 

[STEEZY]

Not saying this is the issue in your case, but I have had a bad batch of Hanna alkalinity reagent before that read high.

Definitely seems like the tap water could be a factor here tho.

 

[Randy Holmes-Farley]

So, here is my dilemma.

I have been testing my tank religiously with the Hanna DKH Checker for the last 2 years. I do not currently use a Salifert or any other brand DKH checker to validate the test results of the Hanna checker.

I have prepared three 5 gallon buckets of salt water for a 15 gallon water change today. I measured the DKH of my tank at 10.2 DKH and then went to check the DKH of the fresh salt water. This was prepared with the Red Sea Blue Bucket Salt, I checked the ICP analysis of the batch that I received and according to their ICP analysis the DKH of the salt should measure out to 7.868. I did not use RODI water as I was cutting corners today (I know, mistake on my part).

After testing the DKH of each bucket of fresh salt water the results were as follows: first bucket - 11.1 DKH, second bucket 11.3 DKH, third bucket 11.4 DKH. All three results were higher than what the ICP analysis of the bucket batch listed. I ensured that I recalibrated my refractometer and double checked that the salinity of each bucket came out to 1.025. I also used a fresh container of Alk reagent (lot 0159) to see if there was maybe an expired reagent issue, no dice there.

Besides the obvious of going out tomorrow to buy a secondary DKH checker to confirm the accuracy of the Hanna checker, what else can I do here? Is it possible that my tap water is the culprit and elevated the DKH of the water that much from where the bucket of salt said it would mix to? Has anyone else experienced this issue with either the Hanna DKH checker or with the Red Sea Blue Bucket of salt coming out higher than advertised?

Thank you all in advance!

ICP never gives alkalinity. If they provide it, it was determined in a different way.

Tap water often has elevated alk, as folks note.

 

[Dakoda]

Are you using tap water or RODI filtered water?

If using tap water all bets are off. The salt mixes assume you are starting with RODI.

I was being lazy last night and poured in tap water as our local water is USUALLY low TDS. (I know, amateur move)

This morning I am brewing up a fresh batch of RODI water for a test of 5 gallons to see where the alk will sit at.

Not saying this is the issue in your case, but I have had a bad batch of Hanna alkalinity reagent before that read high.

Definitely seems like the tap water could be a factor here tho.

I double checked the reagent, I have had this issue in the past and went and got a fresh vial of reagent to see if maybe that was my issue and got similar results. I think the Hanna checker is correct this time.

ICP never gives alkalinity. If they provide it, it was determined in a different way.

Tap water often has elevated alk, as folks note.

This was where I got my figures for DKH. 2.81 meq/l converts to 7.868 DKH. Although I think I have figured out the source of my error, I got a new bucket of salt and as I said earlier I was rushed in prepping this batch of fresh saltwater. I did not take the bag out and mix the salt before using. Red Sea claims less than 4% difference between top and bottom of the bucket, but I feel as though stratification may be the source of my discrepancy here.

I am currently brewing up fresh RODI water and have vigorously mixed up the salt for a good 5 or so minutes. I will post up the new reading once the RODI and salt have been mixed!

 

[Dakoda]

I was being lazy last night and poured in tap water as our local water is USUALLY low TDS. (I know, amateur move)

This morning I am brewing up a fresh batch of RODI water for a test of 5 gallons to see where the alk will sit at.


I double checked the reagent, I have had this issue in the past and went and got a fresh vial of reagent to see if maybe that was my issue and got similar results. I think the Hanna checker is correct this time.

This was where I got my figures for DKH. 2.81 meq/l converts to 7.868 DKH. Although I think I have figured out the source of my error, I got a new bucket of salt and as I said earlier I was rushed in prepping this batch of fresh saltwater. I did not take the bag out and mix the salt before using. Red Sea claims less than 4% difference between top and bottom of the bucket, but I feel as though stratification may be the source of my discrepancy here.

I am currently brewing up fresh RODI water and have vigorously mixed up the salt for a good 5 or so minutes. I will post up the new reading once the RODI and salt have been mixed!

Alright guys, results are in!

I checked with a fresh batch of RODI and heavily mixed up the salt bucket and with my salinity hovering around 1.026 I am reading a DKH of 8.5 with the Hanna DKH checker. Seems to me that the issue here was me and my impatience last night and I've learned a bit of a lesson!

Thankfully I didn't use the high alk water last night for the water change and decided to do some reading and sleep on it!

 

[Randy Holmes-Farley]

Sounds good.

Happy Reefing!

 

[Simon_M]

Stratification of the salt, e.g. not being/staying mixed properly. RS say that you only need a minimum quantity of the blue bucket salt for the content to match the ICP test. Not sure about that, because LFS recommends tumbling the salt before use, so YMMV.

Mixing up water for a DT probably uses a whole bucket (or more), so variations between the top and bottom will be all mixed up anyway. Doing a 10% water change (as an example) isn't going to throw things off (by much) regardless of how much there is a difference in the new mix.

Over a year my water will have been replaced five times and probably the thing that matters most is long term stability. If dKH doesn't drop outside a range e.g. below 8 or above 12 is it something to worry about?

 

[Reef.]

Stratification of the salt, e.g. not being/staying mixed properly. RS say that you only need a minimum quantity of the blue bucket salt for the content to match the ICP test. Not sure about that, because LFS recommends tumbling the salt before use, so YMMV.

Mixing up water for a DT probably uses a whole bucket (or more), so variations between the top and bottom will be all mixed up anyway. Doing a 10% water change (as an example) isn't going to throw things off (by much) regardless of how much there is a difference in the new mix.

Over a year my water will have been replaced five times and probably the thing that matters most is long term stability. If dKH doesn't drop outside a range e.g. below 8 or above 12 is it something to worry about?

the salt settling thing I’m not sure I go for, I think it came about because even today most salt don’t match their stated parameters exactly, so back in the day it was probably even worse, saying the salt had settled was a good way of shifting the blame.

 

[Simon_M]

What you get in a bucket of salt will (probably) fall within the manufacturer's stated parameter limits (only) because (as a RS ICP result shows) the specification has very wide tolerances. LFS recommends tumbling salt (probably) because they use a different (cheaper) brand in their own tanks.

 

[Simon_M]

For the Hanna Test Kit, they do recommend using deionised water and not RO/DI water when doing tests. The logic in not using RO/DI is that it may get the TDS down but removing 95% is still leaving 5%. An example where this really does matter is their Calcium Test. My TDS for RO/DI is about 14, for bought deionised water (not expensive) it is 0 TDS. I keep two squeeze bottles of labelled RO/DI and deionised for washing out test vials, syringes etc. and for dilution type tests, respectively.

 

[Randy Holmes-Farley]

For the Hanna Test Kit, they do recommend using deionised water and not RO/DI water when doing tests. The logic in not using RO/DI is that it may get the TDS down but removing 95% is still leaving 5%. An example where this really does matter is their Calcium Test. My TDS for RO/DI is about 14, for bought deionised water (not expensive) it is 0 TDS. I keep two squeeze bottles of labelled RO/DI and deionised for washing out test vials, syringes etc. and for dilution type tests, respectively.

Your RO/DI effluent should not be 14 ppm TDS. It should optimally be 0 ppm TDS.

Yes, the calcium test kit is poorly designed, IMO, to be hypersensitive to trace amounts of calcium in the blank.

The use of RO/DI is fine in most other Hanna kits, IMO.