Petco Aquarium Reef Swirl Stones Gravel AccentsOur Petco Gravel Accents provide a splash of color to complement any tank, bowl, or aquarium. These accents add depth and beauty to your undersea garden. Aquarium light flickers off of this colorful array of stones for added dimension. Made of non-toxic, fish-safe materials and colors. Safe for use in freshwater and marine aquariums.