MG: 1. Add with the 2ml syringe 2ml of water to the test vial. 2. add 4 drops of MG-1 and swirl gently for 30 seconds. 3. Add one spoon of Mg-2 powder (spoon inside) to the test vial and swirl for 10 seconds. 4. Place the plastic tip firmly on the 1ml syringe and draw into this MG-3 reagent until the lower end of the black syringe part is at the 1.00 ml mark. Ensure that during this that the plastic tip is submersed in the Mg-3 reagent to avoid that air bubbles are withdrawn instead of liquid. An air layer between the liquid and the piston is normal. This is air which was present between the end of the tip and the piston, this will not influence the result. 5. Start adding the Mg-3 reagent with the 1 ml syringe to the test vial until the color changes to gray or blue (whichever color is observed first). Do this drop wise and swirl after each drop for a second or two. 6. Hold the syringe with the tip facing upward and read the position of the upper end of the black syringe part. Each division corresponds to 0,01 ml. The magnesium concentration can be obtained from the table or by use of the following equation: ppm Mg = (1 - reading step 6) x 1500 Natural sea water has a magnesium concentration of approx 1300-1500ppm. The cencentration varies with salinity. Too low magnesium concentration makes maintaining correct and alkalinity concentration difficult. Magnesium cencentration can be incread with Salifert's magnesium.