Many people do not like the toxicity and odor of water treated with chlorine and prefer other methods to keep their pool safe.   Heavy use of strong chemicals on a regular basis is not environmentally friendly.  The feel and taste of a non-chlorinated pool appeals to a majority of people.

Salt Generators

Chlorine is created by a salt generator that transforms a tiny bit of added salt in the pool.  Chlorine need not be routinely added.  If the pool becomes dirty a treatment with chlorine or other oxidizing chemical will be needed. With salt generators the ph tends to get high so it needs to be analyzed regularly. Decrease the ph with muriatic acid.

Bromine is nice for tender skin and has no bad smell but it is more pricey than chlorine. It also needs to be added more often because it burns off quickly in sunlight.    After mingling with harmful contaminants bromine continues to work where as chlorine becomes deactivated.

Ozone

Impurities react with ozone, a form of oxygen which is active.  Contaminants combine with ozone gas dissolved in water and oxidized them the same way as chlorine.   Because it makes them join together, they are easily removed form filters.  Chlorine use can be reduced by 60% to 90%.

Copper and Silver

The fact that algae is killed by copper and bacteria and viruses are killed by silver is commonly known.   They have long been used to clean water.   After ionization by a very small amount of electricity copper and silver react with the pollutants in the water destroying them.

The bacteria and algae join together so they are easier to remove from the filter.   A systematic shock of swimming pool chlorineor a non-chlorine oxidizer will be needed but routine chlorine usage will be greatly reduced.