Here the ammonia and nitrite are chemically changed and removed along with the proteins and any floating waste products. The double ventilation ensures that the remaining ozone is quickly converted into oxygen thus ensuring that only clean, oxygen rich water returns to your pond. This water is so oxygen rich that the sides of the pond start to work as a complete biological filter. An ideal situation for your fish should the electrical supply fail temporarily. Other positive effects.
Ozone is also an ideal gas to combat germs and bacteria.
No known bacteria is resistant to ozone thus enabling you to keep your system under control. Eventual outbreaks of disease forming bacteria flow through the filter and are killed instantly before they can cause any damage. These bacteria are always looking for a host such as a fish. This is in contrast to nitrite producing bacteria that don't float around but attach themselves to the sides of the pond, and the biological part of the filter. Because of the oxygenation of the water they will then multiply thus creating an ideal balance.