Glamor Stone have an artificial casing and may therefore only be rinsed briefly with COLD water before use. So DO NOT wash the gravel with hot water and not warmer water than the aquarium water is. It is pH neutral and using a special resin and does NOT release substances into the water and is guaranteed to be non-toxic. The gravel meets the requirements of DIN EN 71 and can therefore be regarded as non-toxic. These trendy glamor stones make it possible to match the right color to your aquarium. Whether you want natural colors or more cheerful colors everything is possible with Aqua D'ella Glamor Stones.