Koi

Peter May says...

All pond life needs oxygen, including at the bacterial level. But oxygen does not dissolve readily in water and in order to increase this potential it is necessary to expose as much of a surface area of the water as possible to the oxygen. Any process that moves water about in the open air gives it the chance to absorb a little of the oxygen in the atmosphere. This can be done by creating droplets from a fine fountain, which must be the most cost-effective method of achieving oxygenation. Unfortunately, fine fountains are at the mercy of wind and local turbulence, casting the water adrift from the pond. There are styles of fountain jet that use energy from a pump to suck water and mix in air at the same time. These gushing, frothing jets send up a column of white water that is as much a mixture of air and water as you can get. Because of the strength and volume of the column of water, the jet is less prone to being blown by the wind. Waterfalls are also good, especially those that splash water about. You may feel that you have enough oxygenating plants in the pond to sustain the biology of the pond during the day, but at night, when oxygenators stop oxygenating, you need an extra supply to sustain the fish and the bacteria. However, if you run an extra oxygen supply night after night, the pond environment will get used to it. Soon the wildlife and bacteria in your pond will need it all the time.