"... The filtration system should include a recirculating pump, an external bio-filter and a UV sterilizer or an ionizer. An external pump is preferred over a submersible pump, ....The bio-filter will help remove muck and debris from the water during recirculation...."
Additionally with all the activity of numerous dogs, we installed sod on the terraces and pea gravel, 5' wide around the pond perimeter. Description from landscapemagic.net. I searched for this on bing.com/images