Pond Aeration

Koi needs oxygen and so does the bacteria in the biological filter. Dissolved Oxygen level of 8 mg/litre in water temperature of about 25 deg C is almost ideal since it is almost at saturation point. I used a TetraPond water test kit to measure this. Plants (including algae) in the water also uses oxygen at night. Plants take in carbon dioxide and produce oxygen only in the day, during photosynthesis.

Besides the natural absorption that occurs at the pond water surface, any ways to agitate the water artificially will increase the oxygen absorption by the pond water. Pond designers often include a waterfall for aesthetic reason, as well as for pond aeration. Waterfalls also create the soothing sounds of gurgling water in my home. Waterfalls are ideal for informal pond design. Plants and rocks formation can create a beautiful natural setting. In the picture of my second pond (below), my waterfall is almost fully hidden by the plants (a large bird-nest fern, money plant(Epipremnum aureum), water pennywort and backed by heliconia rosetta).

In my third pond, I used a pot of over-flowing water that sits on a shelf. This then cascade down into the Koi pond through a small step down, bounded by pandan plants(Pandanus amaryllifolius). Other forms of water-feature designs are commonly used as well in Asia, most with feng-shui themes.

Some pond keepers uses an air pump with an air-stone (normally placed within the filter chamber to create streams of bubbles before the biological filter chamber). I don’t use this method in my ponds.

Instead, I use the venturi pipes (picture above). The venturi pipes are very cost effective in aeration. Water from the return pumps are forced through the venturi pipes at high speed and draws air down the air vent to create lots of bubbles at the outlet.

The 2 photos on the top show the construction of my venturi pie. One photo shows the view as seen from the outlet.

Placement and location of the venturi pipes is important. Where feasible, the pipes are arranged to circulate water slowly in a clockwise direction around the pond (circulation is supposed to be good for Koi) and moves dirt and debris in the pond towards the bottom drains using the centrifugal effect. The pipes should be placed about 4 to 6 inches below the water surface, not too deep as it will not work properly if placed too deep (unless you have a strong enough water pump!)