Yes According to China Aquaculture Network, anhydrous calcium chloride aquaculture has residual chlorine, because anhydrous calcium chloride can dry chlorine. When anhydrous calcium chloride comes into contact with chlorine gas, it will absorb moisture in chlorine gas, thus drying chlorine gas. This reaction is a chemical reaction to absorb water, which is called hydration reaction. In this process, calcium ions in anhydrous calcium chloride will combine with moisture in chlorine to produce calcium chloride and water.