GloFish Multicolor Fluorescent Aquarium Gravel adds depth and beauty to complete your GloFish experience and complement your fish. Gravel specially selected to stand out under the blue lighting in your GloFish aquarium. Use as substrate or accent to fully customize the look of your aquarium. For optimal results, use two pounds of gravel per one gallon of water. Rinse gravel before using. Five-pound bag.