What is carbonate hardness (KH or CH), and how do I test for it?

Carbonate hardness is a measure of carbonates and bicarbonates dissolved in water. It refers to the ‘buffering’ ability of the water, which is how the water maintains a stable environment for aquatic life.

To determine carbonate hardness you need to measure total alkalinity. This can be done using a photometer and Palintest Alkalinity tablets, known as Alkaphot (AP188). Visual methods to measure total alkalinity are also available.