JBL ProCristal i30 FilterSponge 1xClean water, healthy fish: spare filter sponge for JBL ProCristal i 30Clear aquarium water: change filter sponge every 3 months.Optimal cleaning: 30 ppi porosityOptimal biological filtration: promotes the colonization of useful cleaning bacteria.Included in delivery: spare sponge for JBL CristalProfi i 30, ProCristal i30 FilterSponge