The 7 balls are pressed fertilizing pellets, enriched by a special process with all the nutrients vital for aquatic plants, especially iron and trace elements. The nutrients are released slowly, providing a very favourable depot effect. The ball shape permits the convenient use in existing freshwater aquariums. Specially suitable for the specific nutrient supply or post-fertilization of aquatic plants which mainly absorb their nutrients through the roots, such as echinodori, cryptocorynae and others.