Magnesium Testing Troubles

[Hooloovoo]

Sorry for the long post, but I wanted to be sure to provide all the relevant details.

I have been having trouble with my Magnesium Test Kit (Red Sea Pro Magnesium). Their documentation clearly states that, if you used more than 0.8 mL of the titrant, you probably missed the endpoint of the titration, and should repeat the test. I used 0.84 mL of titrant when I tested. Red Sea's chart only goes up to 0.8 mL (1600 ppm), but it was easy to extrapolate that 0.82 mL would work out to about 1680 ppm.

This seemed really high, so I repeated the test two more times. Each time I tried to be more precise than the previous attempt, but I still came up with the same result. Unlike the Red Sea Pro Alk test kit, the color change point in the Mag Pro kit seemed very sudden and distinct to me, so I don't think it was an issue identifying the end point. My full tested parameters were as follows:

Temp: 80 F
Salinity: 1.026 s.g.
Alk: 7.58 dKH
Ca: 396 ppm
pH: 8.07
Mg: 1680 ppm

I next decided to mix up a fresh batch of Saltwater with Fitz Reef Pro Mix (The display tank water was mixed with Aqua Forrest Reef Salt) and test it. I left the freshly mixed SW to circulate overnight, and then tested Alk, Ca, pH, and Mg the next morning to establish a baseline. Before testing Mg, I went out an watched Red Sea's YouTube video on how to use the test kit, an made sure to follow it exactly. Results as follows:

Temp: 80 F
Salinity 1.025 s.g.
Alk: 8.27 dKH
Ca: 458 ppm
pH: 8.0
Mg: 1640 ppm

My question is whether the reading of 1640 ppm is most likely the result of a bad test kit, something wrong with my procedure that I have somehow failed to see, or is it really that high in both my Aqua Forrest mixed display tank and my fresh-mixed Fritz RPM SW? If the readings are accurate, should I be concerned that they are this high?

 

[saltyfilmfolks]

I liked this video the best. Vivid
and most folks hate the Mag test.
I dont think that mag is an issue in the short term.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, many people get excessively high readings with this kit.

 

[blazedmasta]

Sorry for the long post, but I wanted to be sure to provide all the relevant details.

I have been having trouble with my Magnesium Test Kit (Red Sea Pro Magnesium). Their documentation clearly states that, if you used more than 0.8 mL of the titrant, you probably missed the endpoint of the titration, and should repeat the test. I used 0.84 mL of titrant when I tested. Red Sea's chart only goes up to 0.8 mL (1600 ppm), but it was easy to extrapolate that 0.82 mL would work out to about 1680 ppm.

This seemed really high, so I repeated the test two more times. Each time I tried to be more precise than the previous attempt, but I still came up with the same result. Unlike the Red Sea Pro Alk test kit, the color change point in the Mag Pro kit seemed very sudden and distinct to me, so I don't think it was an issue identifying the end point. My full tested parameters were as follows:

Temp: 80 F
Salinity: 1.026 s.g.
Alk: 7.58 dKH
Ca: 396 ppm
pH: 8.07
Mg: 1680 ppm

I next decided to mix up a fresh batch of Saltwater with Fitz Reef Pro Mix (The display tank water was mixed with Aqua Forrest Reef Salt) and test it. I left the freshly mixed SW to circulate overnight, and then tested Alk, Ca, pH, and Mg the next morning to establish a baseline. Before testing Mg, I went out and watched how to use the test kit, an made sure to follow it exactly. Results as follows:

Temp: 80 F
Salinity 1.025 s.g.
Alk: 8.27 dKH
Ca: 458 ppm
pH: 8.0
Mg: 1640 ppm

My question is whether the reading of 1640 ppm is most likely the result of a bad test kit, something wrong with my procedure that I have somehow failed to see, or is it really that high in both my Aqua Forrest mixed display tank and my fresh-mixed Fritz RPM SW? If the readings are accurate, should I be concerned that they are this high?

I'm in the same boat. I think the issue is the 10ml syringe not accurate. Test and see if you pulling the correct amount of test water from the tank.

 

[BlueCursor]

I use this and my values were very close to values I got when I sent my water out to be lab tested. That company that provides the kits to mail in samples. Can't remember the name at the moment.

I don't use the 10 ml syringe. I use a digital pipet. Not that you need it. The key here with the syringe I think is to align the black rubber rim that touches the inside of the syringe with the 2 ml mark. Don't align the bottom of the black pointy tip with the 2 ml mark. If you look at the bottom of the syringe, assuming it is exactly like the one that came with my kit 4 years ago, the bottom is concave and the rubber tip is pointed. So you definitely want to align the black ring that touches the inside of the syringe, not the black tip, with the 2 ml mark. If you have been aligning the tip point, you are adding too much sample and this is why your readings are higher.

Make sure you are adding a single drop at a time when you get close to the end of the titration amount. Be very very careful. Also, I add just enough so the liquid doesn't appear to have any red tint left. Purple color requires one more drop for me, then I stop.

Hope that helps.

 

[Hooloovoo]

I use this and my values were very close to values I got when I sent my water out to be lab tested. That company that provides the kits to mail in samples. Can't remember the name at the moment.

I don't use the 10 ml syringe. I use a digital pipet. Not that you need it. The key here with the syringe I think is to align the black rubber rim that touches the inside of the syringe with the 2 ml mark. Don't align the bottom of the black pointy tip with the 2 ml mark. If you look at the bottom of the syringe, assuming it is exactly like the one that came with my kit 4 years ago, the bottom is concave and the rubber tip is pointed. So you definitely want to align the black ring that touches the inside of the syringe, not the black tip, with the 2 ml mark. If you have been aligning the tip point, you are adding too much sample and this is why your readings are higher.

Make sure you are adding a single drop at a time when you get close to the end of the titration amount. Be very very careful. Also, I add just enough so the liquid doesn't appear to have any red tint left. Purple color requires one more drop for me, then I stop.

Hope that helps.

Thanks for the info. Everything I have read so far, and every video I have watched affirms that I am performing the test procedure correctly. The only thing I see that could be throwing things off would be a lack of precision of the 2 mL syringe I am using to measure out the sample. I will try comparing it with some of my syringes from other test kits to see if there is a noticeable difference.

 

[BlueCursor]

Drawing 2 ml with a 10 ml syringe is bund to introduce inaccuracies. Do you have a 1 ml syringe? If so, try using that to add 2 ml to your test vial. Just draw and dispense 2 1 ml samples into the test vial. See what your results are then.

 

[Hooloovoo]

Drawing 2 ml with a 10 ml syringe is bound to introduce inaccuracies. Do you have a 1 ml syringe? If so, try using that to add 2 ml to your test vial. Just draw and dispense 2 1 ml samples into the test vial. See what your results are then.

I have 1, 2, 5, and 10 mL syringes, but I don't really use the 5 or 10 mL ones for anything requiring precision. I have tons of the 1 mL syringes, and that's mainly what I use; but in this case, I used one of the 2 mL syringes. My thinking being any imprecision in the 1 mL measurement would be doubled if I used it to measure out 2 mL. The 2 mL syringe, however, uses a plastic stopper instead of a rubber tipped one. I thought that could make some difference, so I decided to measure out 2 mL using the 1 mL syringe and the 2 mL syringe, and then compare the results. There was no perceivable difference in volume. Of course all of this is hobby grade stuff, so there is a limit to how precise you can be with it.

I went ahead and ran the test one more time using the 1 mL syringe to measure out the sample this time just because. I also made sure the tip on the syringe I used to measure out the Mg titrant C was on extra tight, which I had not paid special attention to before. The result was that, this time, I used 0.81 mL of titrant, which works out to 1620 ppm. I feel confident that the test has been performed as precisely as it possibly can be, and that the result is accurate within the limitations of this test kit. Thanks to everybody who replied for the sanity check. Maybe I will try a different brand of test kit in the future for comparison sake. If anyone has another brand they think I ought to try, let me know.

 

[dragon99]

I've been pretty happy with the Salifert Mg test. It's pretty straightforward and has been fairly close to my triton results (+-20ppm I think).

 

[dew9000]

Had the same issue and did all the same things. Decided to go back to Salifert test kit after only 5 uses of the Red Sea kit. Salifert measured right in line with normal readings around 1320. There was no way a freshly mixed batch of Salinity salt I was using at the time was over 1600 since it has lab tested batch values on the side of the bucket. I wonder if there are kits out there with 1 or more bad reagents. Seems like some people have no issue.

 

[GoVols]

I've been pretty happy with the Salifert Mg test. It's pretty straightforward and has been fairly close to my triton results (+-20ppm I think).

+1
The Red Sea Pro mag was giving me high readings and my intake stopped. Tried the Salifert kit and my mag was 100ppm lower than the RSP. Dosed up mag to the Salifert and my intake kicked back in.

Also the Salifert is a whole lot quicker test than the Red Sea to perform.

 

[GoVols]

FWIW, many people get excessively high readings with this kit.

+1

 

[Cornerboy]

I'm having the exact same problem Hooloovoo. I've run the test 3 * tonight and 3 times 2 days ago all of my readings we're right at the top of the chart. I took my water into the local fish store where they performed the exact same test. Their results or that they magnesium was only 1100.

 

[Spieg]

FWIW, many people get excessively high readings with this kit.

Old thread I know, but I'm currently having the same issue with my Red Sea Pro Mg Kit (always comes out at 1550-1600+ ppm). Maybe the reagents are old? The kit was purchased only a few months ago, but who knows how long it sat on the shelf before I got it. I'm ready to chuck this one and try a different test kit. Any recommendations for a more reliable Mg kit?

 

[dragon99]

Old thread I know, but I'm currently having the same issue with my Red Sea Pro Mg Kit (always comes out at 1550-1600+ ppm). Maybe the reagents are old? The kit was purchased only a few months ago, but who knows how long it sat on the shelf before I got it. I'm ready to chuck this one and try a different test kit. Any recommendations for a more reliable Mg kit?

You will have better success with the Salifert or Aquaforest Mg test kits. I've used both and have no complaints.

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