How to measure carbonate hardness (KH) of a freshwater aquarium

To measure the carbonate hardness (KH) of my aquarium I use the JBL KH test kit which contains:

1. One vessel where to insert water
2. Reagent
3. Instructions

It is very easy to find the KH value for a freshwater aquarium, all you have to do is to put 5ml of aquarium water into a vessel and add drops (one drop at a time) of reagent until the colour of the water changes from blue to yellow, every drop represents 1° dKH (carbonate hardness – german scale).
For a freshwater aquarium the recommended level is: 3-8 ° dKH.

More details about Carbonate hardness and the relationship between Kh, PH and CO2 you find on the page freshwater aquarium water testing kits.