Although a still, calm pond can be a beautiful, relaxing feature of your garden, it also has its problems. And those problems arise because that stillness means a lack of aeration. An attractive way to get the water moving is with a waterfall, but will a waterfall aerate a pond, or is there more to it?
A waterfall will aerate a pond, but it has its limitations. If your pond is small and shallow, a waterfall might create enough circulation to cover the entire volume of water. However, if you have a large, deep pond, a waterfall will likely be inadequate on its own, and you may need extra help.
There’s more about pond aeration and the extent to which a waterfall can do the job below. You can also learn how to overcome the limitations of using a waterfall for aeration. So, if you want to get to the bottom of it, dive in.
What is Pond Aeration?
Aerating your pond involves moving the water around so that more of it comes into contact with the air. That contact increases the transfer of oxygen from the air to the water.
Once transferred, the oxygen dissolves into the water, oxygenating the pond.
So, aeration is the means of increasing the amount of dissolved oxygen in the water.
Why Does a Pond Need Aeration?
There are two main reasons for aerating your pond:
Dissolved Oxygen Sustains Life
Dissolved oxygen is what sustains pond life. Oxygen is just as vital to life below the water as it is above. Without adequate supplies of it in your pond, your pond’s health and the life it supports will suffer.
It’ll leave your fish gulping for air at the surface, trying to get oxygen from the atmosphere. That’s because they can’t get enough from the water, and without oxygen, they’ll suffocate.
As well as increasing life-sustaining oxygen levels, aeration discourages excessive algae growth. When that growth is extreme, it’s known as algae bloom. Too many algae in your pond will turn it a nasty green color and cause bad odors.
Increasing Dissolved Oxygen Helps Control Organic Waste
But, excessive algae doesn’t just look and smell bad. It also reduces oxygen levels.
As part of the natural process in a pond, when the algae die, aerobic bacteria feed on them and other decomposing organic matter. They break down that waste matter, preventing it from building up in the pond.
But, as more algae grow and die, providing more nourishment for the aerobic bacteria, those bacteria multiply.
This becomes a problem because the aerobic bacteria use up dissolved oxygen. But, in an un-aerated pond, the oxygen isn’t replaced quickly enough to keep up with demand from all the living organisms that need it.
As the oxygen levels deplete, aerobic bacteria die off. Anaerobic bacteria in the depths of the pond take over. But, they are less efficient and take longer to break down organic waste.
The organic debris continues to build up, regardless of the slower pace at which the anaerobic bacteria is breaking it down. The result is you’re left with that familiar sludgy mess that accumulates at the bottom of the pond.
And let’s not forget the smell. The smell and the waste build-up are signs of disruption in the delicate balance of life in your pond.
So, proper aeration to increase oxygen aids your pond’s natural processes. It enables aquatic life to thrive in a balanced ecosystem that keeps the build-up of organic waste under control.
So A Waterfall Aerates a Pond Because it Moves the Water?
Yes, it does. And no, it doesn’t. Confused? Well, allow us to explain.
How a Waterfall Provides Aeration
A waterfall feature isn’t only an aesthetic audio-visual adornment to your pond. It can also provide means of aeration by the movement of water it creates.
First, as the water drops, it takes in oxygen from the atmosphere. As that oxygen-laden water lands in the pond, it increases oxygenation.
Second, as the water lands, it displaces the pond water at the base of the waterfall. That movement exposes more pond water to the air, facilitating the transfer of oxygen from the air to the water.
Why Isn’t Aeration From a Waterfall Enough?
There are a few reasons aeration from a waterfall isn’t enough:
A Waterfall Creates Limited Surface Area Movement
The problem is that the water movement from a waterfall only occurs within a confined area. That is the water surface around the base of the waterfall.
If your pond is small, that may be OK. But, if you have a large pond, water movement from the waterfall is unlikely to radiate across the whole surface area.
A Waterfall Doesn’t Move Water at the Bottom of the Pond
Unless your pond is very shallow, water movement from the waterfall won’t extend right down to the bottom of it.
An inadequate degree of top to bottom water circulation results in layering or stratification of the water.
It means you end up with oxygen-infused layers at the top and oxygen-deprived layers below. It’s a particular problem, the deeper your pond.
The limited depth of water movement from a waterfall means it does little, if anything, to avoid stratification.
What’s the Result of This Limited Aeration?
So, particularly if you have a large deep pond, it will only be partially aerated by a waterfall. That will leave a good part of it untouched and exposed to the issues discussed above.
With only a small area of your pond aerated, you’ll likely find your fish congregate around the waterfall. That’s where the dissolved oxygen levels are the greatest.
While this looks great aesthetically, it means you have an oxygen problem in the rest of your pond.
Also, if your pond becomes stratified, fish and other pond life will struggle to survive in the oxygen-deprived lower layers. All you’ll get there is a build-up of slimy organic waste.
How to Ensure Adequate Pond Aeration
The good news is this doesn’t involve getting rid of your waterfall. It’s still a valuable means of aeration. But you need to recognize and accept its limitations.
That means giving your waterfall a helping hand to boost aeration throughout your pond.
After all, if your fish spend all their time around the oxygen-rich waterfall, large areas of the pond will be unused. That’s like buying a four-bedroom house but living in one room. You might as well not bother.
So, to boost the aeration in your pond, at and below the surface, consider adding a submersible aeration system.
A submersible aeration system has an advantage over adding another water feature. That’s because it aerates from the bottom of the pond upwards, moving the lower oxygen-deprived layers to the surface to take in oxygen.
So, aeration occurs through the entire column of water, not only in the top layers. The constant circulation can disperse oxygen throughout the whole pond. That makes it more effective than the surface aeration of a waterfall.
An excellent example of such a system is the Aquascape 75001 Pond Air 4 (available on Amazon). It comes with four aerators to space around your pond. That gives you the flexibility to maximize the area covered to suit your pond’s needs.
If you have a smaller pond, you may not need the coverage of four outlets. In that case, you can get the two-outlet version, the Aquascape 75000 Pond Air 2 (also available on Amazon).
Both of these systems are relatively inexpensive for the benefit your pond will receive. It’s also simple to set up and run, as you can see from the following video.
Conclusion
So, a waterfall will aerate a pond. But the aeration is limited mainly to the nearby surface layers of the water.
Adding a submersible aerator is an effective way to provide aeration throughout your pond. It’ll aerate from the bottom up, not just across the water surface.
Although they’re an added expense, your pond and the aquatic life it supports will thank you for it.