Is ICP magnesium test accurate?

[Miami Reef]

I will echo what Randy said. I find Red Sea test kits to report extremely high values on ICP. Definitely do not stop at first color change. Make sure you go at least 3-4 drops past that to get a “complete” color change for more accuracy.

That will make the result even higher lol

 

[Reefahholic]

That will make the result even higher lol

The least amount of titration used (stopping at first color change) makes the value/test result appear “lower” than what it actually is. So we would think the target is “too low” and dose up. As a result, the ICP may come out to be 50-100 mg/L over the actual target. This is why I said to make sure to go to complete color change (more titration used) which shows a “higher” result, and you would likely dose “less.” This should be closer to the actual target level on ICP.

 

[Miami Reef]

The least amount of titration used (stopping at first color change) makes the value/test result appear “lower” than what it actually is.

The issue is that the Red Sea test reads way too high.

 

[Reefahholic]

The issue is that the Red Sea test reads way too high.

For me the test kit itself reads low, but on ICP it’s way too high, because I’m correcting based off the low reading. Same happens with the Red Sea Calcium test kit for me. It’s a little confusing, but I think you understand. If my test result came out high, I wouldn’t correct, or there would be less of a correction, and therefore the ICP value would be closer to target.

Lately when I get a result I dose back 1/2 the amount required and it’s coming back closer to target.

 

[X-37B]

I have used Salifert for a long time and the results were close enough when I ran an icp. I have no experience with red sea except for the calcium which reads the same as the Salifert does.
I do know from the RedSea calcium test that when the color changes you need to wait 10-20 seconds to make sure the color holds.

 

[Reefahholic]

I have used Salifert for a long time and the results were close enough when I ran an icp. I have no experience with red sea except for the calcium which reads the same as the Salifert does.
I do know from the RedSea calcium test that when the color changes you need to wait 10-20 seconds to make sure the color holds.

Yeah, I never waited. Does it need to hold. Maybe that is my problem. This is why I hate most hobby grade test kits. I do like Hanna Checkers because they give you a number, and they’re close to ICP.

 

[Miami Reef]

My salifert was within 20-30 below ATI.
That said, "Is ICP accurate for Mg" is a bit too vague. Sent one sample and got 1280 to 1480 for different ICP vendors.



So I'd just call yours 1340 +-60 ppm, that is - close enough.

Hi @taricha


I tested my magnesium with salifert at the same that I collected the sample to send to ATI ICP.


Salifert: 1425ppm

ATI ICP result: 1436ppm

That’s much closer than I was expecting! I currently really like salifert. Thanks for recommending it to me!

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for posting this comparison.

 

[areefer01]

Is it true that ICP is not accurate with magnesium? I was under the impression that ICP was especially accurate with major elements.

Have you reached out to the ICP vendor? I use ATI as well but have not really crossed reference across test kits - I'd probably go crazy. I don't use it for this but since you mentioned it and being curious I did a quick check using my last result from 7/17/2023. I forget what the trident is for +- on Mg but I think I recall it being 15 ppm.

Mg:
Trident: 1253 ATI: 1314

Alk:
Trident: 8.47 ATI: 8.78

Ca:
Trident: 442 ATI: 429

Phosphate:
Hanna: .48 ATI: .38

Nitrate:
Hanna: 4.4 ATI: 4.39

I use Tropic Marin Pro Reef which reports Mg in the range of 1300 - 1350 assuming I mix it correctly.

 

[jason2459]

I guess for me the question is not if it's accurate but is it accurate enough? I'd say most likely.

Here's some of my past testing comparing Mg results.

Big 3 Shootout Alk, Ca, Mg: RedSea, Nyos, Elos, Salifert, API, Hanna, Triton, AWT

It's finally down to the big three. Alkalinity, Calcium, and Magnesium. This will most definitely be the last big set of comparison testing I'll be doing as it covers all the basics of what I at least periodically test for along with the Nitrate, and PO4 shootouts done previously. My previous...

www.reef2reef.com

Triton vs. Aquamedic AWT vs. Hobbyist kits API Salifert Elos RedSea Hanna etc

Here it is the last Show Down. This time around I'm looking to see how Aqua Medic AWT stacks up. AWT started out around 2006 and I've never heard anything spectacular about them but in 2014 Aqua Medic bought them out and is now Aqua Medic Water Testing. And just recently Marine Depot started...

www.reef2reef.com

Saltmix Parameters bring on the test results

There was an excellent thread put together quite some time ago now by Billybeau1 and hilgert. I've referred to it may times to see if someone is close to the expected values of a particular saltmix. There can of course be slight variations and if any settling has occurred in the mix before use...

www.reef2reef.com