Bromine is chemically very similar to chlorine. Bromine compounds tend to react more slowly than chlorine compounds so bromine is generally more stable and less subject dissipation in sunlight. The dissociation of hypobromous acid into the bromine ion is less affected by pH than the corresponding reaction of chlorine. This makes bromine active over a larger range of pH than chlorine. Bromine will combine with ammonia to form bromamines similar to chlorine but unlike chloramines, bromamines are effective bactericides and do not produce the degree of odor and eye irritation associated with chloramines. Bromine is less affected by high temperature and nitrogen wastes than chlorine so it is particularly attractive for use in hot water spas. Bromine is more expensive than chlorine and has not yet received widespread acceptance by swimming pool operators.
The form of bromine most commonly used in pools and spas is the organic chemical bromo-chloro-dimethylhydantoin which contains both bromine and chlorine. It is marketed under various trade names and is generally in tablet form for use in erosion feeders..

Bromine residual should be maintained between 2 and 4 ppm.