Ozone is used as a disinfectant to kill bacteria and other harmful microorganisms that may be present in the water. Ozone is injected into a venturi through which water is flowing. The micro bubbles created by the venturi allow the ozone to go into solution and begin the disinfection process. The contactor vessel is designed to give the ozonated water several minutes of retention time before mixing with the untreated water in the biological filter tower. Biologically detoxifies the water by converting ammonia to nitrites, and nitrites to nitrates.
Biological filters convert toxic ammonia, from fish waste, to non-toxic nitrate.
A media is used that serves as a home for the two types of bacteria required to convert ammonia. Water recirculating through the sand filter and protein skimmer combine to flow over the media of the biological filter. The biological filter also serves to remove gasses like carbon dioxide and ammonia that may be in solution. The agitation of water flowing across the large surface area of the filter allow these gasses to be removed. Phosphates are removed by plants, algae or with frequent water changes.