This natural product is particularly suitable for the constitution of new basins and ensures that the water in existing basins is healthy. Maerl increases the hardness of water and stimulates the development of microorganisms that ensure a correct biological balance in your pond. Dosage: For the constitution of new basins with a substrate layer: mix 50 ml of mearl per m² of pond surface with the substrate before the pond is filled with water. When filling the basin, add another 75 ml per 1000 liters to the water. Dosage for an existing pool: 75 ml per 1000 liters. In both cases, mix 75 ml to 5 liters of water in a watering can and distribute the mixture evenly over the surface of the pond water.