Super Naturals™ by CaribSea Our pre-washed Super Naturals™ are designed with your success, and ease of use in mind. Packaged in sizes that make sense, most types are available in both 20 and 50 pound bags. We have carefully selected different sizes and colors for you, to help you create a natural underwater environment. These inert products will not affect your pH or alkalinity, allowing you to adjust both of these important water quality parameters any way you wish. While these can be used for marine aquariums, keep in mind you will have to use standard buffers, our aragaMilk™, or aragaMight™ to keep your alkalinity and pH up where they need to be. Marine Sand - An inert, natural substrate. Recommended for freshwater aquariums with external filtration. Very striking. Do not use with undergravel filtration. Grain Size 0.1 - 0.3 mm.