Kh Professional New Test Kit


For the very accurate determining of alkalinity (KH)

The carbonate hardness (KH) or alkalinity of a water sample characterises the buffering capacity, i.e. the ability to maintain the pH value of the water. There are many terms in water chemistry to describe the buffering capacity with varying definitions. The term “carbonate hardness” is customary in fishkeeping; however, it is the alkalinity which is measured. In this test, both terms are used synonymously. The reading for alkalinity is usually given in degrees of German hardness (°dH).

The alkalinity should be tested in all aquariums with great regularity. If the alkalinity in the aquarium is too low, the pH value can sink (sudden drop in acidity) to a level which is life-threatening for many fish and invertebrates. In reef aquariums, an adequate alkalinity level is essential for strong coral growth. On the other hand, an overly high alkalinity in saltwater tanks can lead to calcium carbonate precipitates and also have a negative impact on coral growth. The alkalinity in saltwater aquariums should range from 6 to 9 °dH. The alkalinity in freshwater aquariums should not fall below 3 °dH.

The Tropic Marin® KH/Alkalinity-Test Professional is a high resolution test kit for the determination of the alkalinity with a resolution of up to 0.1 °dH per titration; including a conversion table to other units. Easily recognizable colour change from turquoise blue to pink.


  • Measurement range: 0.1 – 20 °dH
  • Accuracy: 0.1 °dH
  • High-precision determination of alkalinity in aquaria
  • Sufficient for approx. 100 applications at a KH of 10 °dH in the water and a resolution of 0.2 °dH / or 50 tests at 0.1 °dH resolution
  • Measured on the German hardness scale (°dH)
  • Conversion Table for other units in the instruction manual included

How to use:

  1. Shake the bottles before use!
  2. Rinse out the glass cuvette with tap water and then several times with aquarium water.
  3. Fill the glass cuvette with exactly 5 ml of aquarium water using the dosing syringe.
  4. Then add 3 drops of reagent A (indicator) and swirl the cuvette carefully. The water sample will turn turquoise.
  5. Place the enclosed dropper tip on the small syringe and draw out 1 ml reagent B (titrator).
  6. Now add reagent B from the syringe to the water sample drop by drop until the water changes colour from turquoise to dark-blue and violet and finally to a clear pink colour. Swirl the cuvette after each new drop. The measurement is complete when the sample has reached a clear pink colour without any blue tinge.
  7. The consumption of reagent B (difference of 1 ml) multiplied by 10 constitutes the alkalinity in °dH.
    Example: If the lower side of the syringe plunger is at 0.28 ml following titration, then the consumption of reagent B is 0.72 ml (difference of 1 ml). 0.72 x 10 = 7.2. The alkalinity of the aquarium water is 7.2 °dH. It is possible to carry out the test with a 2.5 ml sample so that the test reagents last longer or for hard water over 10 °dH. If you choose to do this, follow the procedure described above and multiply the consumption of reagent B by 20 following titration.
  8. Rinse out the glass cuvette and the syringe thoroughly with tap water after the measurement process

How to correct unfavourable values:

To increase the alkalinity when levels are too low, we recommend using Tropic Marin® TRIPLE BUFFER or LIQUID BUFFER for saltwater applications and Tropic Marin® RE-MINERAL TROPIC for freshwater applications. If the alkalinity level is too high in your saltwater aquarium, we recommend using Tropic Marin® ALCA-BALANCE.

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