Magnesium

[jason2459]

Sorry, I didn't read all the posts here but fwiw: It is entirely possible for the person performing and analyzing the ICP results to get the Mg number wrong but so far that's been one of the most reliable numbers I've seen come out of ICP-OES testing but still about +/- 50mg/l accuracy. It's also generally the same for at home testing with most Mg test kits except for when using Red Sea's. That is as long as the test is performed properly and the reagents are good. Making sure the color change is complete and not stopping to soon is important.

As for using an ICP-OES results of the major elements to calculate Salinity I have found to be inaccurate and usually lower then actual Salinity. Some times it's close, usually it's with in 2, and sometimes more.

 

[domination2580]

The problem with testing new saltwater is every bucket is going to change with all parameters to some extent. That holds true to every brand I've tried. I wonder if you let someone else test the water if they'd test the same results.

Done that. It was the same results.

 

[Scott.h]

Done that. It was the same results.

I use the Salifert mg test. I tested my water last week, right before scooping up water for triton. It measured 1350 if I remember correctly. My triton test results will post today or tomorrow. I've also heard cal and mg are the 2 most likely things to be inaccurate with the hobby grade test kits. I'll let you know how they match up.

 

[Scott.h]

Just got it. It measured 1446. Higher then I want. Also 100 off Salifert. I'm very meticulous when I test.

 

[jason2459]

you could be off by -50 and they could be off by +50... So, sounds pretty close to me.

 

[Scott.h]

you could be off by -50 and they could be off by +50... So, sounds pretty close to me.

im not off by 50, the test is off by 50 lol

 

[DMan]

this entire thread is confusing as hell. Was it the tank water, or new salt water. Was it thier test or yours. Wow.
There is 3min I'll never get back. All for 150ppm of Mg.

 

[Randy Holmes-Farley Verified Community Expert]

There are so many issues with these comparisons that I can't see any problem worth worrying about. lol

The simple fact is every number mentioned for magnesium is OK for a reef tank, and there's no reason to expect them to agree with one another.

 

[domination2580]

New saltwater, my tests show 1500 but af icp test says 1350 when the sample they used was 34 ppt salinity and, mince was 33 ppt

 

[domination2580]

There are so many issues with these comparisons that I can't see any problem worth worrying about. lol

The simple fact is every number mentioned for magnesium is OK for a reef tank, and there's no reason to expect them to agree with one another.

Thanks for joining in sir. I agree as far as nothing to worry about but if new saltwater is 1500 for a water change its just going to keep my mag high. But since it isn't high, icp shows it's 1350, how can I monitor my mag at all in order to use components 123 from af using an equal dose of my mag doesn't drop? What are my options for testing mag if red sea, 3 different salifert tests show 1500+ of mag? Waiting for af test kits to be available but for now what do I have for possibilities for getting an accurate test for magm

 

[Randy Holmes-Farley Verified Community Expert]

The Red Sea magnesium kit reads excessively high for many people.

I'd just dose the recommended amount based on the calcium and alkalinity demand.

 

[domination2580]

The Red Sea magnesium kit reads excessively high for many people.

I'd just dose the recommended amount based on the calcium and alkalinity demand.

Even though mag uptake could be lower than alk and cal?

 

[Randy Holmes-Farley Verified Community Expert]

Even though mag uptake could be lower than alk and cal?

It is much lower. A good two part, such as B-ionic, takes that into account and has the magnesium already in the calcium part. A separated two part like my DIY just has that same amount as a separate additive.

 

[domination2580]

It is much lower. A good two part, such as B-ionic, takes that into account and has the magnesium already in the calcium part. A separated two part like my DIY just has that same amount as a separate additive.

Could you by chance send me a link to your diy two part? Af uses 3 part, I believe it is alk, cal and mag in 2 and 3 is the other essential elements. The instructions say to dose the same amount for all 3. Would you happen to know if their components are figured in as well like the other two parts?
Also, what would you recommend for test kits that really work for mag.

 

[Randy Holmes-Farley Verified Community Expert]

Could you by chance send me a link to your diy two part? Af uses 3 part, I believe it is alk, cal and mag in 2 and 3 is the other essential elements. The instructions say to dose the same amount for all 3. Would you happen to know if their components are figured in as well like the other two parts?
Also, what would you recommend for test kits that really work for mag.

I presume they know what they are doing, and I published my recipe before folks came out with their own commercial 3 parts, so they had some guuidence if they wanted it.

here's the recipe, and places such as BRS sell it or modified forms of it:

An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2006-02/rhf/index.php

Jason has a comparison of magnesium kit, but I don't have the link handy (I'm sure he does)

 

[jason2459]

Having the "My Threads" link is very handy.

https://www.reef2reef.com/threads/b...os-elos-salifert-api-hanna-triton-awt.234660/

 

[domination2580]

Having the "My Threads" link is very handy.

https://www.reef2reef.com/threads/b...os-elos-salifert-api-hanna-triton-awt.234660/

Wow great write up! I'm waiting to get the af test kits to try out and am looking forward to comparing them to red sea and salifert.

 

[jason2459]

Wow great write up! I'm waiting to get the af test kits to try out and am looking forward to comparing them to red sea and salifert.

Thanks. With the Salifert make sure to get a complete color change and not stop on the initial color change. I believe I got images of each stage and what color to look for to stop at. The Red Sea Mg kit is one of the few hobby kits I found to be highly inaccurate. Even after being accurate. Another forum member and I swapped multiple kits and water samples. My red sea kit was way off to start with. His was not and read the test samples just fine. It then became highly inaccurate for me and him after just a few tests. It was not a testing procedure error. The reagents seem to be very volatile for some reason is my only thoughts. I still need to write all that up as I have quite a bit of data points for it from me and him. I have a lot I still need/want to get done. Time...

 

[domination2580]

Thanks. With the Salifert make sure to get a complete color change and not stop on the initial color change. I believe I got images of each stage and what color to look for to stop at. The Red Sea Mg kit is one of the few hobby kits I found to be highly inaccurate. Even after being accurate. Another forum member and I swapped multiple kits and water samples. My red sea kit was way off to start with. His was not and read the test samples just fine. It then became highly inaccurate for me and him after just a few tests. It was not a testing procedure error. The reagents seem to be very volatile for some reason is my only thoughts. I still need to write all that up as I have quite a bit of data points for it from me and him. I have a lot I still need/want to get done. Time...

I know the feeling... I've got a comparison I'm going to attempt to do myself...[emoji6]