Decorative Ornamental River Pebbles Rocks for Fresh Water Fish Animal Plant Aquariums, Landscaping, Home Decor etc, Black Color, 10lbs, 2.0"-3.0" Aids in propagation of beneficial bacteria Adds depth and beauty to aquariums, water gardens, ponds and terrariums Made by nature river pebble stone, average size: 3-5mm Safe for use in freshwater and marine For optimum results, use 2 lbs. of gravel per every one gallon of water