The Inland Seas Nu-Clear Model 533 is perfect for ponds up to 600 gallons and freshwater and saltwater fish only tanks up to 90 gallons. The 30 square foot 25 micron cartridge has 20% more surface area than other similar filters. The cartridge traps particles larger that 25 microns and polishes the water crystal clear. The cartridge can be cleaned and reused. This filter will also hold 1.5 lbs of activated carbon for absorbing water yellowing compounds and other dissolved organics. Includes pressure gauge and 1.5 lbs. of pre-bagged premium Inland Seas Marine and Reef Activated Carbon.