Which device to measure water hardness?

The correct water parameters in the aquarium/pond depend on the fish population and the plants present. Even if the water looks clear, it can be polluted. If the parameters are wrong, diseases or algae can develop in the aquarium or pond.

How to measure water hardness in a basin, pond or aquarium?

To have a healthy pond or aquarium with conditions close to the natural environment, it is important to regularly check and adapt the water parameters.

What is hard water?

It is a water containing a high quality of minerals. These minerals are usually calcium and magnesium. Hardness can be expressed in French or German degrees.

When we talk about water rich in minerals, we are talking about hard water (high GH). If the water is poor in minerals, we speak of soft water.

How do I know if my water is hard?

In Belgium, you can consult the website of your water distributor, which often gives information on the hardness of the water in your pond.

The level of minerals contained in the water often depends on the collection station and the source. It will sometimes even be necessary to add a softener to reduce the quantities of limestone.

In a pond, it is important to have very hard water to improve the health of your fish and the good nutrient supply for your aquatic plants. This is also the case in an aquarium.

Tests to measure water hardness

There are different types of tests: drop tests and strip tests. These tests are generally easy to use, you can also find many tutorials on youtube.

Here is for example the use of a test case from JBL. Most of the suitcases that this brand distributes are quite reliable. We also use the SERA cases to analyze the water in our customers' ponds or aquariums.

Reminder: pH measures whether a given solution is acidic, neutral or alkaline.

What is the difference between GH & KH?

GH is the total hardness of water. It indicates the total amount of dissolved minerals in the water. The KH hardness only indicates the concentration of calcium and magnesium bicarbonates.

To decrease the GH, it will be necessary to dilute the quantity of minerals. The ideal is to make a mixture of its water with reverse osmosis water which is completely mineral-free.

Depending on the origin and nature of the subsoil, the water may contain more or less high quantities of alkaline-earth salts. As a rule, these are then calcium or magnesium salts. The total calcium and magnesium ions represent the total hardness.

Most fish are easy to maintain with a total hardness of around 8 to 20°dH, but care must be taken to lower total hardnesses that are too high by taking appropriate measures.