Is a Pond Aerator the Silver Bullet for Your Pond Problems?

This is the first installment of a new series of articles we’re calling “Silver Bullet Solutions.” The goal is to outline some of the most important and effective things you can do to keep your pond healthy and beautiful.
A pond aeration system may not be the ultimate solution to all pond problems, but it is among the more effective general purpose influencers of pond health that you can add to your pond. They’re relatively inexpensive to purchase and run, require almost no maintenance, and can improve almost every aspect of your pond’s health.

What is an aerator?

Generally speaking, aeration is taking air from outside of your pond and getting it to dissolve into the water. Some aeration should be designed into every pond from the beginning, usually in the form of a fountain or a waterfall. This works pretty well, as splashing the surface from above with water is surprisingly effective at introducing air into the water. This designed aeration, in my experience, tends to be closer to the minimum amount of air introduction to keep your pond healthy, rather than the ideal amount. For most ponds, especially ponds that are large, deep, or unusually shaped, I strongly recommend adding an aerator into the mix.
A dedicated aerator is a very simple thing. It consists of an air pump that forces air from outside the water down through hoses to dispersal units on the bottom of your pond, sending a stream of bubbles into the pond. As the bubbles rise, they circulate the water and dissolve some of the air into the water. It’s a simple process, but a lot of companies have put some very impressive engineering to work maximizing the effectiveness of these little bubbles (and the efficiency of the pumps). Dedicated aerators range from tiny, single-bubbler units for use in an aquarium to enormous, many-bubbler setups that can effectively aerate acres and acres of water.
For most pond owners the middle ground is, of course, just right. This usually means a single, high-efficiency air pump sending air through two to six bubblers (sometimes called aerator stones). The stones should be placed thoughtfully. The goal is to circulate water and bubbles to minimize “dead” regions of water, especially the deepest parts of your pond and areas that aren’t in the natural flow channel of your water (such as “cul-de-sacs”).

What does an aerator do for me and my pond?

1. Oxygenates

The primary and most important goal of aeration is oxygenation of the water. Dissolved oxygen plays many, many roles in a healthy pond ecosystem. Your fish need it to live, obviously, but so do the beneficial bacteria that break down and remove pollutants, contaminates, organic debris, and the waste that your fish produce. Without sufficient oxygen in the water, the bacteria that are the primary cleaning agent of a well-designed pond’s filtration system cannot work at peak efficiency. This means a less clean, less healthy pond.
Perhaps the biggest advantage of a bubble aerator is that it can oxygenate areas of your pond that are getting less oxygen from your current aeration. This includes the areas that are outside of the normal water flow channels of your circulation system. More importantly, a bubble aerator gets oxygen into the water at the bottom of your pond. This gives the beneficial aerobic bacteria in your pond access to the part of your pond where the most problems can arise due to organic debris settling to the bottom. This settling, with insufficient oxygen, leads to the proliferation of potentially toxic anaerobic bacteria that thrive in low-oxygen environments, and to the sludge layer that they live in.
Oxygenating your pond more effectively with an aerator also means that the dissolved oxygen levels in your pond remain more consistent. Inconsistent oxygen levels are caused by insufficient aeration, which is then exacerbated by a variety of factors inside of and outside of your pond. Temperature fluctuations cause the water to hold more or less dissolved oxygen. Water movement being cut off (power failure, cleaning out the pump, etc.) can cause a big drop in the oxygen levels. Rain can also cause big changes. These fluctuations stress both your fish and the beneficial bacteria that are crucial for keeping your pond healthy.
Algae blooms can be not only a major culprit in exacerbating inconsistent oxygen levels in your pond, but are also one of the more problematic outcomes. A sharp rise in the oxygen levels in your pond is responded too most quickly by the single-called, free-floating algae in your pond. They start to reproduce rapidly to take advantage of the extra oxygen in your pond, and these increased numbers of free algae cause pea-colored water. Then, either the oxygen levels start to fall back down on their own, or the algae over-produce to the point where they themselves drive the oxygen levels down. Suddenly, there is insufficient oxygen in the water to maintain the algae population, and they start to die off in massive amounts. With the lower population, the oxygen levels start to rise again, only now there are large amounts of dead algae in the pond that are breaking down into organic pollutants, causing further problems with your water and feeding into this bloom-and-bust cycle of the free-floating algae population. There are other contributors to the algae bloom-and-bust cycle, especially sunlight and excess nutrients in the water, but maintaining consistent oxygen levels is one of the best ways to combat this major problems faced by many pond owners.

2. Improves circulation

Circulation of your water, like aeration, is something that should be accounted for from the beginning of any well-designed pond. Water enters the pond from a waterfall or fountain, then moves through the pond to the skimmer box or filtration intake, which sends it back to the waterfall. This creates a water movement channel that should do a fair job of circulating the water in your pond. Most ponds, however, will have two major dead zones where water is circulated much less effectively. First, unless the pond is designed in a very particular way, there will be areas of the pond that are further away from the main channel, such as corners, coves, or other oddities of shape. Second, and more important, water tends to flow along the upper third or so of the pond between the waterfall and skimmer. The deeper water of your pond gets much, much less circulation.
Each bubbler that you add to your pond adds an additional vector of water circulation, from the bottom of your pond upward. This directly reduces the dead zone at the bottom of your pond where pollutants and debris will otherwise settle down to contribute to your sludge layer. The upward vector of circulation also complicates the existing channel of water movement, which helps to push circulation into the dead areas around the fringe of your pond. All of this movement of water keeps algae from building up excessively (especially string algae), and also keeps mosquito larvae from making a home in the more stagnant areas of your pond. The upward movement also prevents your pond from having temperature and oxygen gradients. Those gradient layers, with cooler water on top and the warmest water on top are especially exacerbated in summer, with the hot air and sunlight warming only the top of the pond. Differing levels of warmth and oxygen levels cause your bacteria to be far less efficient at cleaning your water, and stress your fish as they move from layer to layer.

3. Breaks up surface tension

The bubbles rising from your aerator not only circulate the water, but also break up the surface tension as they break the surface. This has a few beneficial effects. First, it prevents some water-walking insects from taking advantage of your pond. The most important of these, of course, is mosquitos, which can otherwise use your pond to lay eggs. The lowered surface tension also facilitates gas exchange between your pond and the air around it, getting out the carbon dioxide that your fish produce and even allowing the increased release of some pollutants. Finally, the bubbles are effective at keeping your pond from freezing over completely in all but the very coldest conditions. An ice cap over your pond can cause serious problems with gas exchange, even causing your fish to suffocate in extreme cases. It also prevents some pollutants from dispersing out of the water, building them up over the course of winter. Preventing the ice cap from forming in the first place is the best way to deal with it, as breaking up ice manually is potentially dangerous for your fish.
Aeration isn’t the silver bullet for all pond problems, but there are some problems that it can solve completely, and far more that it can help to alleviate. For how much it helps a pond’s health and how little work and cost it requires, dedicated pond aeration is a worthwhile addition to almost any pond.