Salifert Calcium & JBL Magnesium Test Kits

[nerowolfe]

Recently joined this forum, and new to CRS, but I have been keeping either freshwater fish, marine fish or an aquascape, for over 45 years.

Through this forum I discovered the importance of the Ca:Mg ratio in successfully keeping & breeding CRS, but was dismayed by the accuracy of the Calcium test kits commonly available, (all only differenciate increments of 20ppm), and no Magnesium Test kit (for freshwater), so I went online and researched, and what I found were the Salifert Calcium test kit for Fresh & Salt water, and the JBL Magnesium test kit for Freshwater, both of which had good reviews overseas, and a much better resolution of concentration.

The Salifert I could source locally, (from one of our sponsors), and the JBL, I had to source from the UK. UK post was efficient, more so than the much closer Hong Kong / PRC sources, and I received the kit within 8 days.

I have now used both kits twice and compared their results to the accepted formula, when only using a Calcium test kit alone, and I have to say, the results are quite markedly different.

Using the formula, and using Hagen/Nutrafin gH & Calcium (accuracy of 20ppm), test kits, the water tested as follows:  gH = 8  &  Ca = 60ppm

From the formula & compared against the available spreadsheet calculator, I got the following: Mg = -1.7ppm and a ratio of  -34.6 : 1  What sort of ratio is that!!

I then tested using the Salifert Ca test kit and the JBL Mg test kit and got the following:

   Ca = 50ppm  * the calcium test kit can differenciate to 10ppm

   Mg = 8ppm   * the magnesium test kit resolves 0 to 10 ppm then > 10ppm, with 5 to 10ppm being listed as OK.

This then gives the following ratio:   6.25 : 1  ** now it makes sense, not perfect, but but much better, and a solid indicator of what needs to be addressed.

From my point of view, I now have a better understanding of the true situation, and can work to adjust the ratio sensibly.

What are your thoughts on this?

 

[KeenShrimp]

Hi @nerowolfe,

Firstly, I have no experience with the Magnesium test from JBL. I have however tested every single Calcium test on the market and Salifert is highly accurate.

I am going to hazard a guess that the JBL Mg test is not giving you as accurate results as the evidence lies in your equation that does not balance to meet your GH of 8.

I have to mention that many successful breeders do not worry about the ratios. I however do as it brings out brilliant colouring in shrimp with blue tone IMHO within 3 weeks of correcting the ratio.

Salty Shrimp remineralise ra have a ratio of 3.79:1 which is in the sweet spot.

Your first Calculation by using Salifert Ca-test only where you have a negative value of -1.7 (-1.66) indicates that your Calcium/Magnesium ratio is off- in other words you have a Magnesium deficiency. This however cannot just be rectified by adding Magnesium as I have reverse-manipulated your GH equation and for a GH of 8, your Calcium is too high for a Ca:Mg ratio of 4:1.

GHppm= (Cappm x 2.5) + (Mgppm x 4.1)

GH 8 = 143.2 ppm from test kit table

Your Ca = 60 ppm as tested, if you add Mg to a ratio of 4:1, Ca:Mg will be 60:15, but this will shoot up GH to 14!

If you want a ratio of Ca:Mg of 4:1 in your tank, your Calcium needs to be approx 40ppm and your Mg needs to be approx 10ppm.

If you find the source of your high Calcium in your tank like mineral balls etc, remove a few and with a few water changes over a few weeks, the balance in Ca:Mg ratio will be restored wit SS remineralised.

If you have a heavily planted tank, some plants may be chowing your Magnesium ( unlikely due to your GH).

If you are still not happy with the ratio after a couple of weeks, I will be glad to help you calculate how much MgSO4 ( Epsom salts)  to add safely as the sulphate group is heavy and you cannot just weigh out the weight in milligrams as Magnesium.

 

[KeenShrimp]

I would just like to add the reason why I disregarded the second combination test in your post:

GH is the most stable parameter you have to work with in your tank. Whichever test kit you use, that in combination with either a Ca or Mg test will deliver more stable results. So if your test kit for GH consistently tests GH 8, your ratio mentioned in your combined test that got you Ca 50 and Mg 8, will push the GH to 8.81 ( it will measure as 9 GH on API).

The GH equation has 3 variables: GH, Ca, Mg. I would suggest picking the ones you can most accurately test and Calculate the third. There is a reason why very few companies manufacture Mg- testing kits for FW: the low concentrations of Mg is incredibly hard to measure with a test. Just look at how hard it is to find an accurate Calcium test, and Calcium is 3-5 times higher than Mg in a natural FW Body.

 

Good luck?

[nerowolfe]

Thanks KeenShrimp. I will manage from now on using just GH & Ca test.