Eforcase 100 Pcs Luminous Cobblestones Pebbles Stones Glow in the Dark for Aquarium Fish Tank Gravel Decorations,Fantastic Garden or Yard (Green) When you receive the parcel please kindly put all the pebbles in the sun for about half an hour to make them charge fully for the first time use, then you can watch in the dark, they will glow brightly. They will last the glowing for about 2 -3 hours in the fully dark space. They can charge and glow repeatedly. If you want them to glow all the time in the dark indoor or outdoor please install a UV light above them. They glow Blue Green color in the dark and they are Milk Green color in the day light. They can be used to decorate the home and garden flower pots, to mark paths and walk way or as a border for plant beds or ponds.They can be applied to pool, bar, vase decors, fish tank and Aquarium. It includes 30pcs (about 270g) in one color bag. It's a good option for a gift. They look like natural onyx, they are non-toxic, non-radioactive and completely harmless to aquatic life.