Tropic Marin Calcium/Magnesium Combitest Professional

Test kit

Content: 1 Pc

Delivery to United Kingdom is not possible.

Features & Advantages

  • For saltwater aquariums
  • Calcium measuring range: 300 - 498 mg/L
  • Accuracy: calcium 4 mg/L
  • ​Magnesium measuring range: 820 - 1800 mg/L
  • Accuracy: magnesium: 20 mg/L

Item no.: TMA-300028380, Content: 1 Pc, EAN: 619106283806


Tropic Marin's Calcium/Magnesium Combitest Professional is a test for checking the calcium and magnesium values in saltwater aquariums. All necessary test cuvettes, reagents, dosing syringes and measuring spoons are included in the set. The reagents can be bought as refill packs after they have been used up.

Calcium and magnesium in water

Calcium and magnesium occur naturally in seawater and are vital nutrients for marine life. Therefore they should be present in appropriate amounts in saltwater aquariums as well. Calcium and magnesium are crucial for growth, skeleton formation and a variety of biochemical processes. These nutrients are quickly used up and need to be replenished as needed in order to prevent deficiencies which can result in serious harm.

Natural seawater has a calcium content ranging from 400-410 mg/L and a magnesium content ranging from 1280-1320 mg/L. The ratio of calcium to magnesium is about 1:3.25. You should aim to achieve this level in your saltwater aquarium too.

Instructions for use:

First measure the calcium and then the magnesium concentration with the test kit. Make sure you use the same syringe tips for the same reagents to avoid cross-contamination.

Calcium measurement:

  1. Shake the bottle vigorously before use.
  2. Rinse the glass cuvettes first with tap water and then with aquarium water.
  3. Pour 5 ml of aquarium water into each glass cuvette. Use the dosing syringe to do this. Set one of the cuvettes aside. This will serve as a comparison sample.
  4. Attach a syringe tip to the 1mL measuring syringe with red lettering. Draw up reagent A up to the 20 mark (= 0.5 ml) on the syringe. Add the entire amount to the sample for analyis. Close the glass cuvette with a stopper and gently swirl the solution.
  5. Mix the Reagent B powder with a measuring spoon and add one level measuring spoon of Reagent B to the glass cuvette with the sample. Swirl the cuvette (carefully!) until the powder dissolves. Now the water sample should be light blue.
  6. Attach a new syringe tip to the 1ml dosing syringe with black lettering. Draw up 1 ml of Reagent C.
  7. Add Reagent C from the syringe to the water sample drop by drop. The light blue solution should become colourless. Swirl the cuvette gently after adding each new drop. When the analysis and colour samples are both colourless, you can stop adding.
  8. The amount of Reagent C left in the syringe gives the calcium concentration CCa in mg/L. Get the reading from Table I in the instructions for use.
  9. Any reagent C left in the syringe can be put back into bottle C.

Note: If the solution becomes colourless after the first two drops of Reagent C, you can repeat the process. Reduce the sample volume and only use 4 ml instead of 5 ml! Follow the steps as described - only in step 3 - you will have to use a 4 ml sample per cuvette. At the end of the measurement, multiply the value you read from Table I (Step 8) by 1.25. This value indicates the calcium concentration.

Magnesium measurement:

  1. Attach a clean syringe tip to the 1mL measuring syringe with a green plunger. Draw up 1 ml of Reagent D.
  2. Add 0.4 ml of Reagent D to the water sample. The sample will turn light blue.
  3. Add the remaining Reagent D from the syringe to the water sample drop by drop until it becomes colourless. Swirl the cuvette after each drop. Compare the comparison sample and the analysis sample by placing a piece of white paper underneath and looking into the cuvettes from above. Both should be transparent.
  4. The amount of Reagent D left in the syringe gives the magnesium concentration CMg in mg/L. You can read this from Table II in the instructions for use.
  5. Any reagent D left in the syringe can be returned to the bottle D.
  6. All measuring devices (dosing syringes, syringe tips, glass cuvettes) should be rinsed out thoroughly with tap water after the measurement process.


  • 1 x 35mL Reagent A
  • 1 x 9 g Reagent B (powder)
  • 1 x 50mL Reagent C
  • 1 x 40mL Reagent D
  • 2 x 10ml glass cuvettes
  • 1 x 5ml dosing syringe
  • 3 x dosing syringes 1 ml with attachment
  • 1 x measuring spoon
  • 1 x instruction manual

Our expert Oliver Knott recommends:

Regularly checking the water values is essential for a healthy aquarium!

Brands (Manufacturers): Tropic Marin

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