So now that you have selected a quality waterfall manufacturing company, you will now need to select the correct size for the waterfall filters.   You will want to factor in such considerations as size of pond, length of the stream or cascades, environmental conditions, use and type of water feature.  The larger the pond size, the bigger the Eco fall filter must be.  Also if you plan to have fish, you will want a Eco fall filter to accommodate the wildlife.  The average pond of 7’x9’x2′ deep with 4-7 fish will need a filter weir size of at least 18″ wide.  I would recommend the “Big Bahama”  Eco filter BF2600 with a 26″ weir (34.5”W x 25”D x 23”H), this can accommodate a pump flow of 4000-7000 GPH.  The bio fall filter will have a mesh filter to filter out the sediment, and will have 2 bags of lava rock.  These lava rocks will house micro organisms that you introduce to the system.   They will then create a colony and breed on their own and become self sufficient.  The microbes will eat the algae and bacteria in the water to create crystal clear water.    The end result is a natural, drinkable water source safe for fish, pets and children.