AquaClear's unique CycleGuard protection is achieved by combining multiple inserts with the largest media volume available (over 6X greater than any comparable cartridge). Alternate replacement of inserts preserves sufficient bacteria populations to rapidly re-seed the biological filter after cleaning. Alternate replacement of inserts preserves sufficient bacteria populations to rapidly re-seed the biological filter after cleaning. Foam filter blocks are cut to fit each of the AquaClear Power Filters precisely to trap dirt and debris. May be rinsed and reused to preserve the beneficial bacteria colonies. Foam Foam filter blocks are cut to fit each of the AquaClear filters precisely to trap dirt and debris. May be rinsed and reused to preserve the beneficial biological bacteria colonies. 2-1/2" x 2-1/4" x 1-5/8". Carbon Activated Carbon functions effectively to remove dissolved and liquid waste, medications and dyes. Provides many points for the attachment of nitrifying bacteria. 1-1/2 oz. Amrid Zeolite in specially sized bags for removal of ammonia. For use with freshwater only. 2.1 oz. BioMax Inert ceramic rings promote powerful bacterial growth for biological removal of both ammonia and nitrite.