Dymax Black Bio Sponge (32x12)Dymax Bio Sponge is made of quality non toxic material for both biological and mechanical filtration. Enhances good water quality as a filter media as a site for beneficial bacteria, and efficient as a mechanical filter medium (trapping loose particles of debris). Suitable for both freshwater and marine aquarium. Can be washed and re used (rinse in tank water not tap water to maintain its use as a biological filter).