Aquarium Fish Tank Gravel Marine Pure Water Pebbles Color Rocks - Blue 5 Lbs Gravel for adding depth and beauty to your aquarium Non-toxic, Colorfast Characteristics of Pure Water Pebbles Premium Fresh Water Substrates Grain size range from 3.1mm - 6.3mm. Aquarium Pebbles / Rocks / Stones / Gravel from Pure Water Pebbles. Each bag contains approximately 5 pounds of gravel