Helps simulate a positive, natural environment Promotes the growth of healthy bacteria which breaks down waste Reduces the amount of unhealthy debris in the water Made of non-toxic, fish-safe materials and colors Imagitarium Rainbow Aquatic Gravel livens up any tank with its kaleidoscope of carefree colors. Vivid hues of pinks, blues, yellows and greens complement your splashy fresh or saltwater fish. This aquarium gravel is perfect for creating whimsical displays and maintains the healthy status of your tank.