Our Graphite Slate Ecoscape rock is not only an artistic choice for the home aquarium, but also a safe choice for both fish and plants. Graphite slate rock is a naturally occurring crystalline carbon. Though formed through heat and pressure, it is a soft rock that is inert and will not alter pH or hardness. It comes in a variety of shapes and sizes handpicked by the Ecoscape team to give your aquarium a unique look.