The Weryerker 1/2 Pound Natural Rocks Healing Crystals Home Indoor Decorative Gravel for Decoration, Healing, Reiki, Chakra (1/2 lb White Coral) is made of natural materials that are safe for use in an aquarium environment. These gravels are designed to mimic the look and feel of real rocks, making them a perfect addition to any home. With a variety of colors available, it’s easy to find the perfect match for your aquarium.