TUNAI Decorative White Sand For Aquarium substrate can add a great contrast in colors from other rock or other ambience in your tank. Gravels are one of the most important parts of the aquarium because, it gives a pleasant look to aquarium. They work as a great part of the decoration. The minimum 2.5-inch layer of gravels is very important for the healthy aquarium. Suitable for Fresh water Tropical, Cold Water & Marine Aquarium Tanks. Provide a Very Healthy Environment for Plant & Fishes. How to Use: Empty the sand in a bucket and wash till all the dirt is out and then fill in aquarium.