CHLOR OFF is a chlorine neutralizer for removing chlorine found in tap water. It makes water change risk-free even during winter when chlorine level contained in the water gets higher.Chlorine will irritate the gills of fish and will kill the useful nitrifying bacteria that live in your filter and substrate - causing algae bloom and health problems in fish.The use of Aqua Conditioner Chlor-Off will also neutralize the harmful heavy metals found in the tap water.