What Are Phosphates? Phosphates are a salt of Phosphoric Acid. Phosphates is the main ingredient in fertilizer but also comes from rain water, leaves, bloomed flowers, dog hair and even our own skin. Phosphates became known around the pool industry and households in the 1970′s. People started to use phos-free or low phosphate laundry detergents to help protect streams, lakes and other run off areas from the horrible effects of excessive use of phosphate .