CaribSea Super Naturals Jungle River are high quality gravel substrates designed with your success and ease of use in mind. Sizes and colors have been carefully selected to help you create a natural underwater environment like those of the Amazon River blackwaters or Asian jungles. These inert products will not affect your ph or alkalinity, allowing you to adjust these important water quality parameters any way you wish. Can be used in marine aquariums when alkalinity and pH are properly maintained.