Features: Wash it first， then use it directly into the filter. Immediately you will achieve the nitrifying bacteria which is indispensible for your tank! Do not often change these rings. After six month used， change half of them and use new rings with the rest old ring Wash it with aquarium water before use， do not use tap or boiled water More than 10 times the ability to cultvate nitrifying bateria than normal bacteria house Sea water resistant， will not decompose， suitable for both marine and fresh water aquarium， fish pond and other industries PH Neutral， do not produce any chemical agent Package included: 250g of Bio Ring with net bag