The most common chemical that is used to kill bacteria, living organisms and any other contaminates (such as dirt, debris, and algae spores) that are in pool water. The two most common forms of chlorine are Dichlor (60% granular chlorine) and chlorine tablets called Trichlor. Chlorine tablets may come in Triplex form with the addition of a small amount of Algaecide and Flocculant.