Sodium Bromide

Sodium Bromide works similar to an algaecide, but what it is really doing in the water is combining with free chlorine to produce chloramines. Now, normally, you don't want chloramines in your water. Also known as combined chlorine, chloramines are largely responsible for the objectionable odor of chlorine. Additionally, they are not as good at killing bacteria as chlorine is. However, chloramines are better suited to kill mustard algae than is free chlorine. 

To use sodium bromide, add an initial dose according to label instructions. At the same time, add extra chlorine. A good rule of thumb is that whenever you add  sodium bromide, add a gallon of chlorine at the same time. You need the extra chlorine so that the sodium bromide can use it to form chloramines. Continue adding a smaller maintenance dose for about a month following the initial treatment to ensure that the algae does not return. 

While sodium bromide is effective, try not to use more than recommended on the label and try not to use it for more than a month. Using too much sodium bromide will eventually make it hard for the pool to hold chlorine. 

Sodium bromide is generally packaged as Yellow Out or Yellow Treat or something like that.