JBL Sansibar Dark 5 kgDark substrate for freshwater and saltwater aquariums. Key Features: Perfect hold for plant roots: substrate with 0. 2 0. 6mm grain size for freshwater and marine aquariums and terrariums. Vigorous plant growth: prevents the seeping in of sludge and other waste material with its fine granulation and density. Ideal for fish, invertebrates and plants: no release of unwanted pollutants into the water. Fine granite sand is gentle on the sensitive barbels