Ecosmarte Pool

Numerous alternative devices, many dating back to the late 1980s exist to reduce or eliminate the use of certain pool chemicals. Many of them completely eliminate the use of chlorine stabilizer, (cyanuric acid) and the obvious human health issues.
Ionization
The oldest methods involve copper or copper/silver ionization using ionic metals to kill algae, bacteria and virus. [...]

Chemicals
Chlorine is the dominant form of pool sanitation but Bromine, Bacquacil, and Sodium Tetraborate sanitation has a statistical presence.
Those pools using an alternative form of chemical sanitation will most likely be required to drain the pool to convert back to chlorine or install an alternative sanitizing device. The number of alternative chemical pools is falling [...]