Sand is the most cost effective media. The grade of sand is tightly controlled so only highest quality, triple washed water treatment grade sand is used. The water passes through the sand and any particulates get trapped by the sand. Particles above 40 micron are typically trapped.
Filter Ag has a high surface area and complex flow path for a more efficient removal of suspended matter. Typically particles down to 20 micron can be trapped. Filter Ag is slightly more expensive than sand and should be soaked for 24 hours before use. A 50:50 mix of sand/Filter Ag forms an excellent value media mix.