Penn Plax Undergravel Filter &ndash; Premium Aquarium 4 Filter Plate System Designed to Fit 40/50 Gallon Tanks Undergravel filter system includes 4 filter plates (each measuring 11.5" X 11.5") with extra large 1 inch adjustable lift tubes. Filter is suitable for most 40 and 50 gallon aquariums. Clips to hold each section securely together are included. 2 carbon filter cartridges remove odors, and water discoloration by trapping the pollutants in the pores of the carbon. This undergravel filter hides from view for maximum aesthetics. Safe for use in both freshwater and saltwater tanks. Effortless setup and easy maintenance make this premium undergravel filter a must have for all home aquariums. Simply place filter plates at the bottom of the tank and cover with gravel.