Calcium - Hanna Checker -vs- Salifert

[DWill]

I've been using the Hanna Checker for calcium testing for over a month (me IM Nuvo 10 is about 8 weeks old) it's been giving very consistent results averaging about 405.

I read a thread here on R2R saying basically the Hanna Checker may not be accurate. Since I was getting consistent results I didn't worry too much about it. But, then I started wondering about the reading.

Last week I bought a Salifert Calcium test kit. I tested my water with both the Hanna and the Salifert.
I'm guessing by now, you know where I'm heading with this post.

Three tests done every other day starting a week ago Friday, so Friday, Sunday, Tuesday... Hanna Checker ( 439 - 435 - 421 ) averaged 431 - Salifert, each of the three Salifert tests was 455.

I changed 2 gallons of water Thursday and tested yesterday (Friday) and today.
Hanna Checker (408 - 405) Average 406.5
Salifert test (450 - 445) Average 447.5


I use Tropic Marin Pro Reef. The calcium level in fresh batch at 1.026 is advertised to be in the 440 range.
Alkalinity before the water change was 8.9, after 8.6. I added ESV Alk to the fresh saltwater to get it as close as possible; I didn't check the calcium.

So, the question.... Which test is to be believed... Hanna Checker which is consistent but appears to be low; or Salifert which is consistent and seems to be a close match to what Tropic Marin says a fresh batch of water should be ?

 

[Vu337]

I have both too and I get the same kind of reading s

 

[Ron Reefman]

For my money, I trust Salifert way more than I do Hanna. And I think Hanna tests are prone to a lot more user error. But that's just my opinion based on a lot of Salifert use and some time with Hanna checkers that I ended up selling.

 

[DWill]

Yeah, I think the Hanna calcium checker is going up for sale here shortly

 

[Scorpius]

The only Hannah checker I use is the ULR Phosphorus checker and even it is very fussy on getting an accurate reading. The difference between gently rotating the curvete and shaking it to dissolve the packet can mean the difference between getting 4 or 16 ppb.

 

[Chuk]

I have the hanna checker and I've had issues with getting consistent readings from it. I honestly this it's because of the small sample size and huge dilution as part of the rest procedure.
Another way to state that is it's my fault the kit isnt accurate but I still use it every once in a while but I try my best to be as careful as possible when I do the test.

 

[DWill]

I think you’re right regarding the sample size. even with the now included pipette I think there’s a lot of room for error in other steps of the test. A drop or two too much or too little reagent and/distilled water for instance.

The thing is, at least in my case, I’m getting consistent results. They just seem to be consistently low; but I that indicates the test procedure is consistent as well.

In the end though I think I’m going to switch over to the Salifert test kit. It’s very consistent and the results are more in line with I expect to see based on the salt mix I’m using.

 

[PatW]

I understand that for the calcium test, Hanna has a dilution step. To improve accuracy, you could increase the volume of the dilution step by a factor of 10.

Be that as it may, I believe that natural seawater has a calcium level of 370. Most reefers run calcium high just as a safety margin, Corals can deplete a tank of calcium, but it isn’t going to happen in the ocean.

Both tests are really telling you the same thing. Your calcium level is well into the safe zone.