Fluidized Sand Filters allow for an extremely large surface area, for processing fish waste on an organic level. These are great filters for both saltwater and freshwater aquariums, and will help to drastically keep nitrate levels down. Sand filters are used worldwide by public aquariums, including the Shark Reef at Mandalay Bay Hotel & Casino in Las Vegas Nevada. Of course their sand filters are on a much larger scale, however the fluidized sand bed filter concept is the same. We incorporate sand bed filters on our own reef aquariums at OCReef.com.