Aquaclay F-13-20 should ideally be put in the provided filter medium bags.Aquaclay F-13-20 should be washed under warm, running water before filling the filter. During the first filling of the filter the bacteria need approximately 2-4 weeks to reach about 70% of the filtration performance. After 4-6 weeks nearly 100% of the filtration performance is accomplished. The colonization time can be reduced by using bacterial cultures (bacteria starter).