Can a Waterfall Effectively Aerate a Koi Pond?

The Asian carp species that ornamental koi descend from were able to adapt from lakes and streams to rice paddies, but they wouldn’t do so well in a still water habitat. Chinese aquaculture farmers can raise carp in rice paddies where the water enjoys some form of natural aeration and motion. This is typically accomplished through irrigation and draining. In the case of garden ponds, a few species may be able to withstand a still water ecosystem, but not koi because they need proper oxygenation at all times. Aeration and filtration are some of the most essential koi pond supplies because they keep the water column in motion, thus promoting oxygenation, but there’s more you need to know about this biochemical process.

Pond Waterfalls Aren’t Only Decorative

Seasoned fish keepers will do everything possible to keep a waterfall running in their garden ponds. Some prefer a fountain or a water wheel in conjunction with a filter instead of, or in addition to, a waterfall. These ornamental aeration systems can add a great touch of style to any koi pond, but they all serve the more important purpose of agitating water molecules, a process also referred to as “turning over the water.” Koi and other fish commonly kept in garden ponds cannot survive in stagnant water. Assuming a waterfall is purely ornamental will prompt some pond keepers to turn it off at night, which shouldn’t be the case because aeration needs to be constant, 24/7.

Physical Oxygenation of Pond Water

The easiest way to understand how water turns over is to acknowledge that the bottom of the pond is where the lowest levels of dissolved oxygen are generated. This is why koi swim closer to the surface when the aeration system is turned off. Those water molecules at the bottom need to rise to benefit from the gaseous exchange at the surface. This is the principle of physical oxygenation, which in a garden pond is provided by mechanical means.

Biochemical Oxygenation of Pond Water

Aquatic plants also contribute to the water oxygenation process through biochemistry. In essence, plants increase dissolved oxygen levels through photosynthesis, but they also deplete it at night, which explains why you shouldn’t turn off waterfalls, fountains, or pumps at night. You cannot completely rely on either biochemical or mechanical processes to provide adequate oxygenation—you need both. We’ve had some people tell us, “we turn our pump off at night for 4 hours and the fish are fine”—wrong! They’re suffering from a lack of oxygen and are breathing hard to compensate. If only fish could write a blog to let you know what they go through!

A Single Waterfall May Not Be Enough

Plants alone won’t take care of oxygenation. You’ll need a minimum of an air pump and 20 percent plant coverage. A waterfall would be a welcome addition, but if you’re caring for a pond that holds more than 4,000 gallons of water, your mechanical aeration needs may call for two waterfalls, a combination of fountains and air pumps, or a larger feature that can turn over more water.

Whether you need aeration, filtration, or any other essential pond equipment, you can find everything you’re looking for at Aquatic Warehouse. We’re located in Kearny Mesa, or you can order supplies from our website and have them shipped to you. If you have any questions, don’t hesitate to call us at 858-467-9297 to speak with one of our friendly and knowledgeable representatives.