Most swimming pool owners use one of two chemical disinfectants in their pools: chlorine or bromine. Chlorine, by far, is the most common, though bromine is a perfectly fine alternative. Bromine will last longer than chlorine in a swimming pool, for one. Plus, bromine in a pool is easier, in general, on swimmers' skin. However, there are a few side effects of bromine in swimming pools, including the difficulties involved in switching from bromine to chlorine disinfection.
If you're currently using bromine in your pool, it can be difficult to switch to chlorine if you need to. Typically, a brominated swimming pool will have to be drained and refilled in order to use chlorine. Chlorine will react with even low levels of bromine in a pool and convert itself to an inactive or "used up" state.
Bromine as a water disinfectant is most often seen in indoor pools and spas, because it's highly sensitive to sunlight. Chlorine is also sensitive to sunlight falling on a pool, but it can be protected by a stabiliser like cyanuric acid. Bromine in a swimming pool can also leave a medicinal taste to the water that some swimmers find unpleasant. Also, bromine can be a bit harder to wash off skin after swimming.
Bromine swimming pool disinfectant is more expensive than similar amounts of chlorine. The cost of bromine is a major reason for why it's not often used in private swimming pools or spas, though it's a favourite in indoor public pools. And even though bromine may last longer than chlorine in a pool, the expense of maintaining it can make it cost-prohibitive for many small pool owners. Higher levels of bromine are needed in a pool than those for chlorine.
Bromine needs to be maintained in a swimming pool at between 2 and 4 parts per million (ppm). Bromine is also a close cousin to chlorine, so pool swimmers with sensitivities to chlorine stand a good chance of also being sensitive to bromine. Bromine also dissolves very slowly, so it can only be added to a swimming pool through a dispenser or feeder. And like chlorine, bromine is classified as a hazardous chemical and should be handled with care at all times.