Biological Filters utilize natural bacteria that colonize the polyester filter media which is inside the filter box or barrel. It is located on the outside of the pond where the water comes back into the pond by gravity, and not under pressure. The bio-filter must be located with the outflow above the water in the pond or above the water fall. Some bio-filters put the water back into the pond through a pipe or tubing. Other bio-filters put the water back into the pond or waterfall through a spillway. The spillway can actually be the beginning, or “header” of the falls.
It is recommended that the water is pre-filtered through a Mechanical Filter or a Skimmer. It is further recommended that an In-line Spring Check Valve be installed to prevent back flow or siphoning of the bio-filter in the event of a power outage, or if you turn off the system for servicing.