Perfect hold for plant roots: substrate with 0.2 - 0.6 mm grain size for freshwater and marine aquariums and terrariums. Ideal for aquarium care: its fine granulation and density prevents mulm and other waste material from seeping in. Ideal for fish, invertebrates and plants: no release of unwanted pollutants into the water. Fine granite sand is gentle on the sensitive barbels of the bottom-dwellers. No light reflections full colouring of plants and fish: easily scared animals feel more comfortable and show their full, natural colouring. Contents: 1 bag Sansibar Dark. Not really suitable for undergravel heating cables.