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Adding an oxidizer to a bromine tub will recharge the bromine. Chlorine acts as an oxidizer to bromine, same as mps. The bromine just stays and gets recharged unlike chlorine that disappears. It becomes this never ending circle. That is why you can add chlorine to a bromine tub and it remains a bromine tub. Now if you add bromine to a chlorine tub, you have just converted to bromine.Once a bromine tub, always a bromine tub...until you drain, clean and fill.