Items you will need
Submersible pond pump
Pond hose or piping
Flexible pond liner
A pond containing Koi needs adequate filtration and water circulation for the fish to thrive. Pond owners use waterfalls as a beautiful way to circulate and maintain healthy water for prized Koi as well as to add dimension to the pond and garden aesthetic.
Calculate the size of the waterfall. Since the waterfall will be the source of water circulation, the flow of water must be strong at about 100 gallons per inch of waterfall width. Determine how high the waterfall will be, and design it accordingly so that it fits in well with the garden and is in proportion to the pond.
Create the elevated mound of the waterfall using excavated dirt from the building of the pond, or use rocks and soil. Duild the mound to the desired height of the waterfall.
Dig out a small pond or reservoir on top of the mound that will hold the pumped water before allowing it to fall through into the main pond, then carve out where the waterfall path in the side of mound. Use the carpenter's level to check that the reservoir is completely level.
Cover the reservoir and the waterfall path with an underlay material such as soft sand, newspaper or carpeting after removing rocks or sharp objects to prevent damage to the pond liner. Place the flexible pond liner and secure with the rocks.
Stack waterfall rocks in any design or pattern. Use poly foam as a sealant to secure the rocks and to force the water to flow over the rocks instead of under.
Direct the pump water to the waterfall's reservoir, using a submersible pond pump and pump hose. Once the reservoir has filled, it will spill over the waterfall and back into the pond.