calcium test kits and magnesium

[aussiejohnny]

so i test my calcium again get 420 ..lfs gets 526 ..i analize my test kit and how i do it ..only difference is im putting more than one drop at a time at the start and shaking tube ...i havent dosed since then so i do another test 3 days later ..i do it drop by drop and dont shake just invert a few times all the way to 22 drops and get 440 ..so does shaking not inverting and rushing first drops ..say 4 then 4 then 4 then one drop at a time really make a difference???
only other change is i started dosing mag as water changes wasnt keeping up and it was very low ...have dosed very slowly to get up the dose still a bit to go according to lfs instructions (about 2 thirds dose ) over 3 days i dont have a test kit so cant test for this...trying to work out why this parameter i test for is always different to lfs

 

[Randy Holmes-Farley Verified Community Expert]

Can you clarify how much magnesium you added? I do not believe home testing is accurate enough to gauge dosing and low levels cannot happen without dosing lots of calcium and no magnesium. You may have pushed it very high.

As to calcium, what tests were you and the lfs using?

Have you been adding calcium? What is the salinity and measured how?

FWIW, both calcium values are fine.

 

[aussiejohnny]

Can you clarify how much magnesium you added? I do not believe home testing is accurate enough to gauge dosing and low levels cannot happen without dosing lots of calcium and no magnesium. You may have pushed it very high.

As to calcium, what tests were you and the lfs using?

Have you been adding calcium? What is the salinity and measured how?

FWIW, both calcium values are fimy

 

[aussiejohnny]

my mag was 1195 i bought a bttle of quantum aragonite c ..reccomended to dose to 68 ml over several days i have dosed only 31 mils so far since monday and decided to slow down on it dont wanna over dose and i seem good at that ..my calcium is seachem reef fusion which is supposed to have mag in it ..but ive learned the calculator is inaccurate after over dosing several times both dkh and calcium following its instructions ..now i dose only one mil a day dkh stays around 9 and until this i thought i had calcium around 420 ..
test kit is api ..ive got a hanna checker for alk but i always get weird readings on dkh ..

 

[Randy Holmes-Farley Verified Community Expert]

I would stop dosing magnesium. It is unlikely to be accurate unless salinity is very low. To drop magnesium from 1300 to 1200 ppm would require consumption of more than a thousand ppm of calcium with no magnesium additions.

It is also very unlikely a calculator is inaccurate. What is inaccurate is testing.

What is wired about the Hanna alk reading?

This has more on not measuring magnesium:

Thread 'Just say NO to magnesium testing: RMM is born'

Nov 8, 2023

OK, this thread has been many years in the making, and I'm posting it here since folks in the chem forum are probably already tired of all the threads relating to problematic magnesium testing.

I'm going to propose a method, let's call it the Randy Magnesium Method, or RMM for short. All good methods need a catchy name.

Here it is.

1. NEVER measure magnesium. If it comes free from an ICP, sure, take a look. It's probably fine anyway. Don't buy or use a kit. Chances are the results are not very reliable, and most of the time, if there is a value out of the...

• Randy Holmes-Farley
• Replies: 293
• Forum: Reef Aquarium Discussion

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• 
• 

 

[aussiejohnny]

I would stop dosing magnesium. It is unlikely to be accurate unless salinity is very low. To drop magnesium from 1300 to 1200 ppm would require consumption of more than a thousand ppm of calcium with no magnesium additions.

It is also very unlikely a calculator is inaccurate. What is inaccurate is testing.

What is wired about the Hanna alk reading?

This has more on not measuring magnesium:

Thread 'Just say NO to magnesium testing: RMM is born'

Nov 8, 2023

OK, this thread has been many years in the making, and I'm posting it here since folks in the chem forum are probably already tired of all the threads relating to problematic magnesium testing.

I'm going to propose a method, let's call it the Randy Magnesium Method, or RMM for short. All good methods need a catchy name.

Here it is.

1. NEVER measure magnesium. If it comes free from an ICP, sure, take a look. It's probably fine anyway. Don't buy or use a kit. Chances are the results are not very reliable, and most of the time, if there is a value out of the...

• Randy Holmes-Farley
• Replies: 293
• Forum: Reef Aquarium Discussion

• 
• 
• 

i worked out according to instructions on bttle that if my 1195 was correct what i have dosed should put me in 1250 range given errors id be happy to accept it may be as high as 1300 ..when i dosed according to calculator i ended up with alk close to 11 ..hanna i love all except the dkh one ..cant seem to get it right so the api is simple test kit gives me a reading i can read consistently not as deadly accurate but i know its 9 as i get consistent results and lfs agrees with my numbers ...hanna for nitrate and phosphate is fantastic..all the advise on here has helped heaps ..my tank looks great almost all my numbers are consistent from day to day im truely starting to enjoy this tank not stress out over it all the time ..thanks to you and other members with direct advise that works.

 

[aussiejohnny]

i worked out according to instructions on bttle that if my 1195 was correct what i have dosed should put me in 1250 range given errors id be happy to accept it may be as high as 1300 ..when i dosed according to calculator i ended up with alk close to 11 ..hanna i love all except the dkh one ..cant seem to get it right so the api is simple test kit gives me a reading i can read consistently not as deadly accurate but i know its 9 as i get consistent results and lfs agrees with my numbers ...hanna for nitrate and phosphate is fantastic..all the advise on here has helped heaps ..my tank looks great almost all my numbers are consistent from day to day im truely starting to enjoy this tank not stress out over it all the time ..thanks to you and other members with direct advise that works.

and salinity 1.026 all the time phosphate less than 0.1 closer to 0 most tests ..nitrate at 5 or less ..

 

[Randy Holmes-Farley Verified Community Expert]

and salinity 1.026 all the time phosphate less than 0.1 closer to 0 most tests ..nitrate at 5 or less ..

I’d personally would make sure those do not go lower or raise them by feeding more. :)

 

[JonasRoman]

so i test my calcium again get 420 ..lfs gets 526 ..i analize my test kit and how i do it ..only difference is im putting more than one drop at a time at the start and shaking tube ...i havent dosed since then so i do another test 3 days later ..i do it drop by drop and dont shake just invert a few times all the way to 22 drops and get 440 ..so does shaking not inverting and rushing first drops ..say 4 then 4 then 4 then one drop at a time really make a difference???
only other change is i started dosing mag as water changes wasnt keeping up and it was very low ...have dosed very slowly to get up the dose still a bit to go according to lfs instructions (about 2 thirds dose ) over 3 days i dont have a test kit so cant test for this...trying to work out why this parameter i test for is always different to lfs

The speed or administration of the titrant for a Ca test is not crucial. For a Mg it is though, because in Mg test, we have stronger binding between Mg and the colour agent meaning that EDTA have more competition, so if you perform a Mg test too slow (the titration), then it bounce back and give false high results. But for Ca this is not the case becasue Ca bind more loose to the colour agent, meaning once EDTA has bound Ca it will not bounce back. You can see this by let a titrated Ca test stand, and you will see it keeps its colour, but for a Mg test it goes back after a while. So you can definitely start with a bolus dose when titrate Ca, but ofcourse when you are close to colour transition you have to drop one drop at at time so you do not overitrate and miss the colour change point. But thats obvious for all titration. I have a feeling that its your LFS that is doing wrong as your result (420-440) is much more expectable. Overall, Ca test is very good, because its easy to design a Ca test, and reason of that is that its easy to isolate the Mg ions selectively (By increase pH above approx 11 making MgOH formation, and hence remove Mg from the solution so to speak). Mg test is the opposite, its very hard to isolate Ca ions selectively meaning all Mg tests that are based on a direct Mg titration are inaccurate and unstable. Either you isolate not only the Ca ions but also some Mg getting false low readings, OR you do not succed isolate all Ca ions getting false high readings. Only solution of this is to do titration of BOTH Ca and Mg (summary titration), and then after that do the reliable Ca titration, and Mg is the diff between the sum titration and Ca titration. Thats the standard method getting reliable Mg titration.

Jonas

 

[Peer.Boerner]

The speed or administration of the titrant for a Ca test is not crucial. For a Mg it is though, because in Mg test, we have stronger binding between Mg and the colour agent meaning that EDTA have more competition, so if you perform a Mg test too slow (the titration), then it bounce back and give false high results. But for Ca this is not the case becasue Ca bind more loose to the colour agent, meaning once EDTA has bound Ca it will not bounce back. You can see this by let a titrated Ca test stand, and you will see it keeps its colour, but for a Mg test it goes back after a while. So you can definitely start with a bolus dose when titrate Ca, but ofcourse when you are close to colour transition you have to drop one drop at at time so you do not overitrate and miss the colour change point. But thats obvious for all titration. I have a feeling that its your LFS that is doing wrong as your result (420-440) is much more expectable. Overall, Ca test is very good, because its easy to design a Ca test, and reason of that is that its easy to isolate the Mg ions selectively (By increase pH above approx 11 making MgOH formation, and hence remove Mg from the solution so to speak). Mg test is the opposite, its very hard to isolate Ca ions selectively meaning all Mg tests that are based on a direct Mg titration are inaccurate and unstable. Either you isolate not only the Ca ions but also some Mg getting false low readings, OR you do not succed isolate all Ca ions getting false high readings. Only solution of this is to do titration of BOTH Ca and Mg (summary titration), and then after that do the reliable Ca titration, and Mg is the diff between the sum titration and Ca titration. Thats the standard method getting reliable Mg titration.

Jonas

Been following along. Thanks for this detailed information!

 

[JonasRoman]

Been following along. Thanks for this detailed information!

You are welcome reeferfriend