Salifert KH test

The Salifert KH test is a simple and easy-to-use droplet test; sufficient for up to 200 measurements.

Information about the water test:

• Measuring range: 0.3 - 16 °dKH
• Resolution: 0.3 °dKH
• sufficient for 100 - 200 tests

Carbonate hardness and alkalinity - what is that?

Alkalinity is used to describe the buffering capacity of your aquarium water. It is the amount of acid or alkali that you can add to your aquarium without changing the pH value.

The official unit of alkalinity is mmol/l. However, the unit °dH (German degree of hardness) has crept into the aquarium hobby, although this is actually the official unit of carbonate hardness (KH). Most commercially available tests for determining alkalinity in saltwater aquariums use the unit °dH. In the sea, the average alkalinity is around 6.5 °dH. The terms carbonate hardness and alkalinity can therefore be used synonymously.

In seawater, the buffer capacity is mainly determined by carbonates and hydrogen carbonates. Boron, silicate, phosphate and magnesium also act as buffers to a lesser extent. You can therefore draw conclusions about the carbonate concentration in your tank by measuring the alkalinity.

Why is determining and adjusting carbonate hardness important?

In saltwater aquariums, carbonate concentration plays an important role in the calcification of corals. Their skeleton consists mainly of calcium carbonate. During the calcification process, one carbonate ion is consumed for each calcium ion. This leads to a decrease in alkalinity in your tank.

Other processes that lead to a decrease in alkalinity include the assimilation of ammonium and the conversion of ammonium to nitrate during nitrification.

In contrast, an increase in alkalinity is achieved by the assimilation of nitrate, the decomposition of organic compounds, the fixation of molecular nitrogen, the reduction of sulfate and the conversion of nitrate into molecular nitrogen during denitrification.

The alkalinity and pH in your tank are closely related. The higher the alkalinity, the higher the pH and the smaller the pH fluctuations.

For the reasons mentioned here, you should always ensure that the alkalinity in your aquarium is in the range of 7.0 to 9.0 °dH.