Wet/Dry filters are a must for any aquatic ecosystem, they enhance biological filtration as well as mechanical filtration with the proper pump they will cut down maintenance time and do a much better job than traditional filters including canister filters. These Pro Clear Aquatics units include Bio-Balls, a polishing block, return hose, siphon hose, return valve and all tubing. These filters work for freshwater or saltwater tanks. (Overflow sold separately). If you are looking for a way to step up your filtration then a wet/dry filter might be just what you need. When you purchase a Pro Clear Wet/Dry you are buying products manufactured right here in the USA with one of these best warranties around. If you have any questions about which unit is right for you, don't hesitate to contact us.