The innovative tetra easycrystal filter pack 250300 is suitable for use with the easycrystal filter 250 and the easycrystal filterbox 300 the filter cartridge ensures healthy crystal clear water due to its intense mechanical and biological filtration the double layer of of filter watting with a large surface area reliably removes even the smallest floating particles white side coarse pre filter green side fine filter quick and clean replacement for optimal filtration change out the fi