Hanna/Salifert dKH discrepancy.

[Dawgvet]

First post here so be gentle

I have been using Salifert test kits for years. I wanted to have a back up testing procedure so I purchased a Hanna dKH test. I received the Hanna checker this Friday so I ran one test to familiarize myself with the procedure. I got a reading of 7.4 dKH (which is low for what my Salifert results tend to be). I normally test my parameters every weekend, so I re-tested again yesterday during my normal testing time. My results were Salifert 8.75 / Hanna 7.5 dKH. My last 3 Salifert weekly test result have been fairly consistent at 8.9 , 8.3 and 8.75 yesterday, and the two Hanna results were close 7.4 , 7.5
So, not trying to make this a flaming thread, why the difference? which one do I put more trust on?
Do any of you use Salifert and Hanna and get close results to each other?
Thank you in advance.

PS. Salifert kit is fairly new/not expired and I swirled the Hanna reagent before using in case of settling/separation.

 

[75pxatr]

I gave up on the Hanna checkers several years ago. Not consistent. I trust salifert.

 

[Dawgvet]

Having read multiple threads here, I realize it’s a love/hate relationship with Hanna. I’ll continue to use Salifert as my primary test kit, I just wanted to know if this was the norm. I’ll continue to check using both and see if I get the same deviation each time and come up with an adjustment “formula”. I just wanted to know is my dKH truly 8.75 or 7.5

 

[Adele]

I think that’s a totally valid question and one that I question as well. I bought a Hanna Alk tester during the Black Friday sale and before then never tested Alk, cal or okay, anything other than salinity. Went all by how the tank look. I had a salifert Alk test, but sad to admit, it seemed so complicated I didn’t know if I was doing it right. This was before the days of smart phones and YouTube (showing my age [emoji6])
So I quit that chem lab. Now watching how to videos takes a lot of the confusion out of it, and the new technology is so much easier, but like you, wonder about accuracy. I’ll be curious so see others responses.

 

[dealseer]

My Hanna and Salifert are 1 dKh off too. I’ve never seen a good explanation.

 

[EddieJ]

In my case, Salifert consistently reads about +1dKH higher than my Hanna. This is across multiple bottles of reagent on both. But most importantly, both of the test kits read very consistently and that's what it is all about. consistent and repeatable. Stability is always the main goal, who really cares what the exact real number is? Think about it, most people chase numbers and usually are aiming for parameters that match a tank they want to emulate. The tank they want to emulate is using a test kit as well that is consistent and repeatable, but is that the real number?

 

[dealseer]

I do want to know the real number more closely than 1 dKh.

 

[Mikeand Mel]

Perfect timing, dont want to hijack thread but, having issue with hanna alk ppm checker also. Just received new reagent, tank read 91ppm (5.09 dkh), multiple tests 91, 92, 91ppm.
Decided to test new Reef crystals batch read 153ppm (8.57 dkh).
Do not have other test kits to compare.

 

[dealseer]

Wow, that’s reading way low.

 

[Dawgvet]

In my case, Salifert consistently reads about +1dKH higher than my Hanna. This is across multiple bottles of reagent on both. But most importantly, both of the test kits read very consistently and that's what it is all about. consistent and repeatable. Stability is always the main goal, who really cares what the exact real number is? Think about it, most people chase numbers and usually are aiming for parameters that match a tank they want to emulate. The tank they want to emulate is using a test kit as well that is consistent and repeatable, but is that the real number?

I agree with you in that stability/consistency is the key and not number chasing. I use my corals/watch my tank to evaluate how it is doing. It's just sometimes "inquiring minds want to know"

 

[madweazl]

I had a fairly large delta between the two kits until I started using a syringe to measure the test water in the Hanna. Eyeballing the line on the "cuvette" is difficult in regard to repeatability. Adding 10ml via syringe is much more repeatable and the results are usually within .1 dKh.

 

[Dawgvet]

I had a fairly large delta between the two kits until I started using a syringe to measure the test water in the Hanna. Eyeballing the line on the "cuvette" is difficult in regard to repeatability. Adding 10ml via syringe is much more repeatable and the results are usually within .1 dKh.

I do the same. I've always used syringes when measuring liquids for consistency and did so for the Hanna test.
I realize not two brands are going to get same results. Heck, no 2 test kits from same brand will, but I would have expected a little bit "closer" results.

 

[Dawgvet]

Update:
I just checked the difference between the two measuring kits again. I use Red Sea Coral Pro salt. I usually make a 4 gal water change every Tuesday. I make the batch about 24 hrs in advance of use and have a power head and heater going in the mix bucket. I usually weigh the salt in a scale and add 4 gal RO/DI to a clean bucket. I calibrate my refractometer with a 35 ppm calibrating solution before I use it.
This batch was at 35 ppm and 78 F. According to the bucket at 35 ppm I should be getting 12.3 to 12.7 dKH. The results I got were: Salifert 11.9 dKH and Hanna 10.9 dKH. So it does look like the Hanna is off by -1 dKH from the Salifert (at least my Hanna checker), with the Salifert being closer to what Red Sea says I should be getting.

 

[madweazl]

Wasnt RSCP one of the salts that dropped in alkalinity quite a bit after a short period if left mixing in a bucket? I wouldn't use what is written on the bucket as much of a standard. I just ran tests with both kits and got 8.0 with the Hanna (143) and .51ml with the Salifert (7.5). Given the margin of error of the kits (approx .3dKh for both), that seems completely reasonable. Either way, I wouldnt be concerned about having my alkalinity off by 1 dKh.

 

[dealseer]

I totally disagree with being ok with a full point difference. I just tested with Hanna and Salifert and the results matched exactly.

 

[Dawgvet]

Wasnt RSCP one of the salts that dropped in alkalinity quite a bit after a short period if left mixing in a bucket? I wouldn't use what is written on the bucket as much of a standard. I just ran tests with both kits and got 8.0 with the Hanna (143) and .51ml with the Salifert (7.5). Given the margin of error of the kits (approx .3dKh for both), that seems completely reasonable. Either way, I wouldnt be concerned about having my alkalinity off by 1 dKh.

Yes, I am aware of the Coral Pro salt dropping in Kh and Ca if let to sit for a long period of time (Mfr recommends using it within 4 hrs after mixing). I usually start with room temp RO/DI (68 F) mix it for about 24 hrs, then bring it up to tank temp. I don't tend to get the white haze this way (precipitate) that I used to when I mixed it with warmer water.
My point is that I was trying to figure out which of the two tests kits was "more accurate". I was trying to use a known standard (what the mfr says levels should be at 35 ppm) to gauge which testing procedure is the more accurate results. So, knowing that the KH may drop some after mixing, seems the Salifert is more "accurate" and the Hanna results would need to be "adjusted" by a +1 dKH.

 

[madweazl]

Yes, I am aware of the Coral Pro salt dropping in Kh and Ca if let to sit for a long period of time (Mfr recommends using it within 4 hrs after mixing). I usually start with room temp RO/DI (68 F) mix it for about 24 hrs, then bring it up to tank temp. I don't tend to get the white haze this way (precipitate) that I used to when I mixed it with warmer water.
My point is that I was trying to figure out which of the two tests kits was "more accurate". I was trying to use a known standard (what the mfr says levels should be at 35 ppm) to gauge which testing procedure is the more accurate results. So, knowing that the KH may drop some after mixing, seems the Salifert is more "accurate" and the Hanna results would need to be "adjusted" by a +1 dKH.

I understand where you're going and what you're after, I just dont think either is more right or wrong then the other, nor do I think it matters (1 dKh isnt going to make a difference to the health of your corals). Stick with which ever you like; for simplicity sake, the Hanna is tough to beat. Salifert has been in the game forever and makes quality kits, cant go wrong.

 

[Dawgvet]

I understand where you're going and what you're after, I just dont think either is more right or wrong then the other, nor do I think it matters (1 dKh isnt going to make a difference to the health of your corals). Stick with which ever you like; for simplicity sake, the Hanna is tough to beat. Salifert has been in the game forever and makes quality kits, cant go wrong.

We’re both in agreement with each other about 1 dKH not making a difference. Since this is my first Hanna Instrument it is my fault for not stating that I also wanted to make sure that I didn’t have a defective one. It sounds like a 1 dKH difference is normal between the two test formats