Pure Water Pebbles Freshwater Aquarium Substrate contains all natural gravel with a fish-safe 100% acrylic coating. These attractive pebbles are non-toxic, colorfast, and will not alter the chemistry of your aquarium water.Gravel Grain Size 3.1 - 6.3 mmPremium freshwater aquarium substrateNatural gravel with 100% acrylic coatingNon-toxic, colorfast and will not alter water chemistryPure Water Pebbles are recommended for aquariums, ponds, terrariums, gardens, potted plants, vases, ash trays, crafts and hobbies, architectural surfaces, landscaping designs, and more! Be sure to check out all of the colors available to find the perfect gravel for your needs.