Oyster shells help maintain good GH and KH levels. They have a stabilizing effect on KH and pH. KH indicates the carbonate hardness of the water.
Many people think that rather hard tap water will not cause any problems for the KH and pH of the pond. However, KH acts as an acidity (pH) buffer in the water.
Fish, plants, and the biological filter "consume" carbonate hardness (KH). If the water is not sufficiently renewed, in winter for example, the KH can drop quickly. It also drops quickly during rainy periods, with major consequences for the fish, because the pH can then drop suddenly.
KH is rarely measured in ponds. We often react when there is a problem, so too late, by adding, for example, KH+ powder. But KH+ powder has disadvantages:
- a lot of the powder goes out through the bottom drain and the filter system
- a short-term effect, with major fluctuations in water levels
- you have to constantly measure and add powder
Oyster shells stabilize KH and pH in the long term. They only dissolve when the KH drops and thus play a buffering role on the pH.
Their action does not depend on rain, water changes, or seasons: KH and pH levels remain stable. You only need to add more when the shells are almost dissolved. As a guide, allow one bag per year for 10 m³; the quantity depends, of course, on the factors described above.
Air-Aqua oyster shells are delivered in a bag and are easy to rinse. They are washed with chlorine and then dried, which reduces harmful bacteria, fungi, and germs. They can also serve as biological filter media in a drip system or a multi-chamber filter.
