HOW IT WORKS - The glow in the dark rocks will absorbs and stores light, then they give off light in the darkness, with several hours of bright glow and then gradually dim away. The process will repeat for many years. MULTIFUNCTIONAL DECORATION - these glow rocks stones can be perfectly applied to fish tanks rocks , aquarium gravel, fairy garden decorations,betta fish tank accessories, turtle tank accessories, outdoor rocks decor, yard roads, walkway and more. SAFETY AQUARIUM ROCKS - made of polystyrene resin, non-toxic and no any radioactive elements, will not cause health effects to animals.These are about 500Pcs glow in the dark rocks outdoor, about 20-30mm inches long & 900g (2LB) weight. BRIGHT FISH TANK ROCKS - these fish tank rocks have very beautiful and brilliant colors. Can be used as an excellent decoration during the day, You can appreciate their brightness and colorfulness. BETTER GLOWING EFFECT - Whether you want to illuminate a fish tank or illuminate an outdoor courtyard, these glow in the dark pebbles can ensure the glow you want, bringing your ample light.The darker the surrounding and the more exposure to visible light, the more bright glow can be seen.