How does it work?
A safe low voltage DC current like that of several flashlight batteries is passed through a set of predominantly copper and silver electrodes. As the water passes through the sealed chamber, metallic ions are generated to purify the water. The microscopic action of the ions with the algae and bacteria has two separate stages. First, the algae, bacteria and viruses are destroyed through a change in their enzyme or DNA replication processes. Secondly all these charged particles flock together and thus are more effectively pulled out by the filter. The ions stay in solution until they are used up by this process. Since the water is being sanitized automatically, it is only necessary to test the ion level every couple of weeks. This beats the daily chore of testing and dosing dangerous chemicals.
Of course maintaining regular water balance is required no matter what sanitizer you use. A benefit of ionization is that it is pH neutral (balanced) and therefore doesn't have a negative effect on water balance.
An ionizer keeps the water safe and sanitary by killing the algae and bacteria. Occasionally though you will need to oxidize the dissolved organics like nitrogen and ammonia compounds. When the water becomes dull, it's time to oxidize. See Bionizer’s all-natural ECO-OXIDIZER.