Above ground swimming pool filter systems fall into 3 categories or types. Sand filters, earth filters, and cartridge filters are the choices you have for above ground pools. Each type of filter is practical, but as with any product, they have their pros and cons. From the standpoint of simplicity, cost, and practicality, the Sand Filter System is the most widely used for the last 30 years. Earth filters have come along in the last 20 years, and cartridge filters have hit the market in the last decade.