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). Size: 32 x 12cm (2pcs/bag)