Mg testing discrepancy!! HELP!!

[RC88]

Hi fellow reefers!
Hope everyone is doing well.
Quick one for you all - I have been using a Red Sea Magnesium test kit and have recently noticed that my Mg is at 1100. I bought a Mg dosing product to bring those levels back up - but before adding I decided to run another test. This time I used the 100 ppm option which means using a smaller water sample and my test result read 1400. I have ran 5 tests with both 50ppm and 100ppm and the results differ from one version to the other. Any idea which I should trust or how to proceed?

 

[Saltyreef]

Hi fellow reefers!
Hope everyone is doing well.
Quick one for you all - I have been using a Red Sea Magnesium test kit and have recently noticed that my Mg is at 1100. I bought a Mg dosing product to bring those levels back up - but before adding I decided to run another test. This time I used the 100 ppm option which means using a smaller water sample and my test result read 1400. I have ran 5 tests with both 50ppm and 100ppm and the results differ from one version to the other. Any idea which I should trust or how to proceed?

Could you post a photo of your directions?

 

[Saltyreef]

Actually i found them.
I would use the 50ppm resolution for accuracy as its a smaller resolution so would be more accurate..

 

[RC88]

Could you post a photo of your directions?

Sure. Here you go. Essentially the same directions but comes with a resolution of either 50 or 100 ppm. Which is dictated by either adding 2ml of water for 100ppm reading or 4ml of water for 50ppm reading. The 2ml / 100pm results are all around the 1400 mark. The 4ml / 50ppm results give me a 1100 reading.

 

[RC88]

 

[Saltyreef]

Sure. Here you go. Essentially the same directions but comes with a resolution of either 50 or 100 ppm. Which is dictated by either adding 2ml of water for 100ppm reading or 4ml of water for 50ppm reading. The 2ml / 100pm results are all around the 1400 mark. The 4ml / 50ppm results give me a 1100 reading.

Use the 50ppm, more accurate.

Its like having a thermometer that reads by 20s and one that reads by 1s
The latter will be more accurate.

 

[RC88]

Use the 50ppm, more accurate.

Its like having a thermometer that reads by 20s and one that reads by 1s
The latter will be more accurate.

Ok great. Got it thanks!!! I was just surprised that both methods gave me different results.

 

[Saltyreef]

Ok great. Got it thanks!!! I was just surprised that both methods gave me different results.

Hobby grade test kits have their drawbacks.
Atleast its consistant over your 5 tests....
Thats what youre looking for. Consistancy.

 

[Randy Holmes-Farley Verified Community Expert]

Magnesium testing is often problematic, and the The Red Sea kit seems top of the list of problems reported (IME).

Try the kit on some new salt water before doing anything to the tank.

 

[Pistol Peet]

Hi fellow reefers!
Hope everyone is doing well.
Quick one for you all - I have been using a Red Sea Magnesium test kit and have recently noticed that my Mg is at 1100. I bought a Mg dosing product to bring those levels back up - but before adding I decided to run another test. This time I used the 100 ppm option which means using a smaller water sample and my test result read 1400. I have ran 5 tests with both 50ppm and 100ppm and the results differ from one version to the other. Any idea which I should trust or how to proceed?

Not sure how long you been doing this for so I don't want to offend you however magnesium test kits need the directions to be read thoroughly as when I first started trying to dose magnesium I was doing the test kit backwards for the reading in the syringe my tests were 100% off talk to somebody found out what I was doing wrong and corrected the problem now everything is golden lots of times to when dosing magnesium it takes a lot of magnesium to bring the levels up to where they need to be you don't want to dose too much either though BRS as a calculator on their website for dosing magnesium into your tank I would check that out

 

[Randy Holmes-Farley Verified Community Expert]

when dosing magnesium it takes a lot of magnesium to bring the levels up to where they need to be

While I'm not suggesting the OP has low magnesium or needs to dose, that is a point that many people find shocking.

A 100 gallon reef tank that needs a 150 ppm boost to magnesium needs more than a pound of an ordinary dry powder magnesium additive!

The reason for that is that magnesium actually comprises only a tiny fraction of the weight in appropriate materials, such as magnesium chloride hexahydrate.