Tropic Marin Tropic Marin Magnesium-Calcium Combitest Saltwater

For high precision determination of the Ca and Mg concentration in saltwater

Along with sodium, potassium, chloride and sulphate, calcium (Ca2+) and magnesium (Mg2+) are two key components of natural seawater. Magnesium and, above all, calcium are important growth factors for organisms which form calcareous skeletons, such as hard coral and coralline algae – both elements form the basic substance of the calcareous skeleton. Furthermore, magnesium and calcium are involved in numerous biochemical processes. In saltwater applications, the reduction in the magnesium or calcium concentration caused partly by cellular metabolism and partly by skeleton formation means it is necessary to test the concentration levels on a regular basis and, if required, add more of one or both ions. This makes it possible to guarantee optimum, near-natural living conditions for all organisms and to prevent long-term damage.

In natural seawater, the calcium concentration is 400-410 mg/l (ppm) and the magnesium concentration is 1280-1320 mg/l (ppm). They also have a fixed ratio of 1:3.25 to one another. Due to the chemical and biochemical interdependencies between calcium and magnesium, you should also aim to achieve this concentration ratio in saltwater tanks.

With the high resolution titration test Tropic Marin® Calcium/Magnesium Combitest Professional the calcium and magnesium concentrations can be determined reliably and separately with a resolution of 4 mg/l Ca and 20 mg/l Mg.


  • Measurement range: Ca 300 – 498 mg/l (ppm)
  • Measurement range: Mg 820 – 1800 mg/l (ppm)
  • Accuracy: Ca 4 mg/l
  • Accuracy: Mg 20 mg/l
  • For determining the Ca and Mg concentration in saltwater aquaria
  • Sufficient for approximately 50 applications