Ceramic substrate is highly porous and provides the ideal environment for beneficial bacteria to grow on. Bacteria are necessary in the filtration process and the ceramic substrate acts as a mechanical/biological filter. Large waste particles naturally created by excess food and faecal matter in your aquarium are caught and ingested by the bacteria, therefore removing and reducing the potential toxicity of the waste.Key benefits:Creates biological stability in your aquarium by providing the ideal environment for beneficial bacteriaBiological, mechanical filtration attacks the waste produced in your aquariumSuitable for cannister, internal and wet/dry filtersComes with a FREE netting bag