Filter-Max III Pre-Filter. Prevents debris such as dead fish and plant material from clogging the intake by distributing the suction evenly down the length of the sponge. Maintains the biological filtration when the main filter is changed or cleaned. Can be used with most power heads as a temporary or permanent filter in aquariums, isolation tanks, holding tanks, etc. Prevents small or baby fish from being suctioned into the main filter. Prevents anemone and invertebrates from being suctioned into the filter. Traps larger waste particles, mechanically cleaning the water. Can be used with most outside power filters, canister filters, and power heads. Includes three adapters for use with various main filter intake tubes. Easy to clean. Just rinse and squeeze under cool running water. Can be used in vertical or horizontal position. Sponge size: 4-inches x 2-3/4-inches. Recomended for aquariums over 40 gallons. Surface area of sponge (in square inches) 49.4.