Donât settle for an ordinary gravel. Natural dramatic colors and textures combined with pH support characterize our Coralineâ¢ and Seaflorâ¢ products. These are coarser materials suitable for most undergravel filtration and fish systems or as an accent for finer sands anywhere where elevated pH values are desirable. Consider the Coralineâ¢ products in brackish or Cichlid aquariums (Central American or African). Seaflorâ¢ Puka Shell substrates are great additions to fine sands in reef tanks where animals make their homes by burrowing in the substrate. Jawfish, blennies and burrowing crustaceans will especially appreciate the extra âconstruction material.â Our substrates are purposely engineered and free of impurities such as ash, metals, pesticides, and silica; which allows you to create a safe and beautiful environment for your fish and invertebrates. Precision grading makes system design a breeze! No matter what type of system you are setting up, we have the substrate thatâs perfect for the filtration method and habitat you are creating.