Salifert testing higher dKh than Hanna

[WhiskeyCoffee]

So the other day I got some erroneous readings on my Salifert alkalinity test. First one was 9.6 dKh then two days later it was 12. I also tested a fresh batch of Reef Crystals and it came out 12 dKh. I panicked but everything looked healthy in my tank. Maybe I just screwed up the tests. I asked a buddy if I could borrow his Hanna and he said no prob. This is where it gets interesting. With the Hanna, I got:

Tank: 8.4 dKh
Reef Crystals: 11.0 dkH

So I decided to do another test with the Salifert tonight. Being as precise as possible, I got:

Tank: 9.5 dKh
RC: 12.0 dKh

Is this normal? I have about 3/4 of the Salifert test solution left so I'd hate to find out it's off. I know both tests are subject to human error but I've repeated the tests and got similar numbers all around.

 

[Cory]

Hello, get soem baking soda (sodium bicarbonate) at the grocery store. Go to the pharmacist and ask him or her to weigh out 1.135 grams of baking soda. Get 1 gallon of distilled water or ro/di. Put the soda in the water shake it up. Test your kit with this. It should be close to 10dkh. If not its off.

May not work with hanna as its not titration based. But try them both anyway.

Now you wont be confused.

 

[WhiskeyCoffee]

Hello, get soem baking soda (sodium bicarbonate) at the grocery store. Go to the pharmacist and ask him or her to weigh out 1.135 grams of baking soda. Get 1 gallon of distilled water or ro/di. Put the soda in the water shake it up. Test your kit with this. It should be close to 10dkh. If not its off.

May not work with hanna as its not titration based. But try them both anyway.

Now you wont be confused.

Hm... That's .227 of a teaspoon. Could I just do 1/4 of a teaspoon? How do you figure out x grams of baking soda = x dKh?

 

[Cory]

Hm... That's .227 of a teaspoon. Could I just do 1/4 of a teaspoon? How do you figure out x grams of baking soda = x dKh?

No you cant. Youll still be confused because it can be off a lot. The baking soda needs to be precise, the water not so much. Its a recipe going around by chemists for a long time now. Like mpre than 20 years iirc.

 

[WhiskeyCoffee]

No you cant. Youll still be confused because it can be off a lot. The baking soda needs to be precise, the water not so much. Its a recipe going around by chemists for a long time now. Like mpre than 20 years iirc.

dang, alright. I just feel weird going in to the pharmacy with a white powder and asking them to weigh it... lol...

 

[chipmunkofdoom2]

I'm not sure I understand. What is your concern? Is it that the newly mixed saltwater is much higher than the tank? Or that the Salifert kit produces different results than the Hanna Checker?

 

[WhiskeyCoffee]

Or that the Salifert kit produces different results than the Hanna Checker?

That's what I'm concerned with.

 

[chipmunkofdoom2]

That's what I'm concerned with.

Personally, this would not bother me. These test kits are not always 100% accurate. While it would be nice if they all agreed, it's not unheard of to have two different results from two different testing methodologies. If the Salifert test kit produced consistent results, I would be satisfied.

 

[WhiskeyCoffee]

Personally, this would not bother me. These test kits are not always 100% accurate. While it would be nice if they all agreed, it's not unheard of to have two different results from two different testing methodologies. If the Salifert test kit produced consistent results, I would be satisfied.

That's kind of what I was thinking... All of these tests are prone to human error so I most likely will never know my tank's "real" dKh...

 

[Gareth elliott]

Personally, this would not bother me. These test kits are not always 100% accurate. While it would be nice if they all agreed, it's not unheard of to have two different results from two different testing methodologies. If the Salifert test kit produced consistent results, I would be satisfied.

Also agree The precision of tests is more important than accuracy. Loads of successful reefs anywhere between 7-11 dkh that have stability.
I personally would be more worried if my reef salt differed that greatly from my tank with the same test kit, but that is me. Fwiw i think all the tests have a margin of error of 3-5%.

 

[Cory]

dang, alright. I just feel weird going in to the pharmacy with a white powder and asking them to weigh it... lol...

Lol i had the same concern. Just bring an unopened box from the store ask. They were happy to do it for me. just tell them its for the fish tank.

 

[Cory]

Fwiw 15 years ago salifert was off by like 4 dkh iiirc. I made a big stink. They then supplied alk standards in the box but dont now.

 

[Cory]

Here it is. I was user boxfishpooalot back then

http://www.reefcentral.com/forums/showthread.php?t=1117617&highlight=salifert

It wasnt off 4dkh

 

[Bmezz]

i rely on hanna for alk. salifert for calcium as hanna really tough for me to get accurate. hanna for phos ULR. salfert for mag, strot, amonia, ph.... I think they all have their tolerances but once i use one i stay with it and know if there is difference from test to test not test method to test method...

 

[Peanut]

I use a hanna checker and what I have found is that you have to be very careful when measuring reagents, water, sample to be tested, etc. If you do, I find it to be very consistent.

At first, just like you I doubted the device itself because my readings were all over the place. I basically gave up on it and tried many others. At last year's Reef-a-palooza in Orlando, Hanna had a booth and I spoke to a rep and explained what I was going through (with both Alk and Ca). He suggested to me that if I really thought it was the device I should buy the calibration/reference set for the specific device and if it is the device that will surely tell me, and if it was the device I could call customer service etc. what?!?!? there's a reference set? So I bought them both (Alk and Ca), I believe they were less than $10 and worth a billion in piece of mind. I can tell you the checker reads the reference sets consistently every single time without any doubt.

Hanna chimes in here https://www.reef2reef.com/threads/no-alk-reagent.353524/page-2#post-4454465

Make sure you are accurate with everything you do.

Having said all that, I'm going to run a test of the 1.135 grams of baking soda lol