Although there are almost no Diatomaceous Earth was for a long time the only green alternative with the ability to filter down to 3 microns. It was very dirty and most of the time some of the white powder would end in pool making a big mess.

Sand filter is as old as the Roman Empire, the new twist of using crushed recycled windshield glass allows for the same 3 micron result.

Paper filters are installed by pool builders because they get rebates, filters cost from $40-$120 and manufacturer suggest you replacing filters every 2 years. Paper even with slow flow of variable speed is 7 micron making it the least efficient of all types of filtration types.