The CaribSea LifeRock Nano Arch is a uniquely structured aragonitic rock form designed for reef and marine environments. Features a surface area interspersed with micro and macro pores that create the perfect environment for the natural growth of beneficial, nitrifying bacteria. Made with natural aragonite instead of the commonly used, and often hazardous cement rock. The realistic look of the rock is created by an artificial coating that mimics the natural accumulation of coralline algae after years beneath the waves. Each CaribSea LifeRock Nano Arch offers endless explorative opportunities for your tank inhabitants as well as offering an incredibly natural look with unique and dramatic dimensions to each aquatic environment and is ideal for the propagation of a wide variety of coral frags. The rock is safe for all fish species and invertebrates.