HarryH3
0
DE = Diatomaceous Earth It's a filter media that looks like baking flour. A small amount added to a sand filter can help the filter capture smaller particles than the sand alone can capture. You can buy it at pool stores, Home Depot, Lowes, etc. It's about $15 for a 25 pound bag in this area. 1 bag would last you a very long time since you don't need to add much to sand filter.