A pond filter is an important component for any outdoor or indoor garden pond. Filters provide biological and mechanical filtration, drive the water through a filter medium and expel cleaner water free from ammonia or other waste from plants or koi. A good filter not only keeps water healthy but also keeps it clear. Dust filters vary in price from one hundred to several hundred dollars, but you can build your own with a trip to the iron business that is equally effective. Instructions Cut several dozen holes in the side of plastic dustbin using a drill and a 1-inch hole cut the drill bit….