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Many pond owners now understand the importance of having a good aeration system in place because it provides significant support in managing the pond. Fish are protected, water quality can be improved and maintained, and overall the pond just becomes easier to keep in better shape.
But the question often comes up, what type of aerator would work best in my pond? In this article, we’ll sort out the various types of aerators available today, and discuss where each one will work best.
Pond aeration today commonly uses three types of systems. The first as many people will recognize, is the pond fountain, which emits a decorative stream of water into the air. The second is a surfaced based aerator. This system isn’t as eye catching but it moves a high volume of water, creating a dome like wall of water over the aerator. The third method uses a sub-surface, high diffusion process. Powered by a land based pump, air is driven through a membrane diffuser that sits at the bottom of the pond, and this releases very fine bubbles into the water.
All three methods provide some form of aeration into a pond. As for which one will work best in a particular setting…that will depend on several factors, such as the size and depth of the body of water, and to a lesser extent, the goals or reasons a person might have for installing a pond aerator in the first place.
Why Pond Aeration Is Important For Fish Health And Water Quality
Creating a higher level of dissolved oxygen in a pond is extremely helpful for fish and for water quality.
If fish inhabit the pond, they will typically do alright in DO levels above 5 mg/l and higher. Anything below that and the fish could be suffering.
Oxygen levels, like many things in the pond, are not static. They will rise and fall for various reasons. Warm water temperatures, and particularly those above 78 degrees, will not retain oxygen as well as cooler water can. So it’s best to keep it supplemented with aeration during the late spring and summer periods.
Algae blooms can also affect oxygen levels. During the day the plants release oxygen into the water as they enjoy the photosynthetic effects of sunlight. But at night, these same plants can pull oxygen from the water and lead to rapid crashes which can kill large numbers of fish.
This is why it’s important to note that 5 mg/l is a decent level of DO as long as it’s not stimulated by an algae bloom. In that case, it may lead to a false sense of security. Getting oxygen levels well above this level therefore is suggested.
Fish will typically thrive with good aeration in place. Growth rates and reproduction are both higher and the fish enjoy better vitality and energy, which is a useful trait if you enjoy fishing for them. More importantly though, they’ll be protected through the various seasonal changes and challenges that confront most any fish pond. Rapid oxygen drops are less likely, and the chance of a full-on pond inversion or turnover is greatly reduced.
Aeration Can Often Help With Pond Algae
Many people who install an aerator in a pond, already laden with algae, are amazed when the algae clears up a few weeks later. The key here is that the higher levels of oxygen in the pond, helped to support existing beneficial microbial populations, most of which are aerobic in nature.
Once stimulated, these good little bugs, help to break down nitrites, nitrates, and phosphates, all of which help to feed the algae blooms. As these nutrients become less available for the algae to use as fuel, the blooms will often recede.
Finally, most any pond will fill in over time with organic build up. Dead leaves, dead algae or pond weeds can all lead to a compost like accumulation on the pond bottom. And unfortunately, the bottom is often the lowest area of oxygen in a pond. When oxygen levels increase throughout the pond through the addition of aeration, this muck build up can slowly be broken down by microbes, or at the very least, it’s accumulation rate can be slowed, sometimes significantly.
This vital improvement on the pond bottom will usually lead to better water quality, which includes improved clarity, less odors, and reduced chance of seasonal algae and weed problems.
The Benefits Of A Pond Fountain
When you drive by some great looking large ponds, and particularly those on golf courses or commercial properties, it’s not unusual to see the beautiful spray of water from a fountain cascading through the air. There’s no question pond fountains are very popular and provide a great display.
A pond fountain, as the name implies, creates a vertical spray of water from a floating surface based system. A motor, vertically positioned, will spin a prop that drives water up through a series of nozzles. It’s the nozzles that create the various patterns you see in the air. There is usually some type of doughnut shaped float that keeps the whole assembly suspended and the motor as well as the intake pipe will lie below the surface.
Fountains can vary a lot in terms of their power, and with various fittings or nozzles the spray pattern can be adjusted to suit many tastes. Normally fountain motors are rated by horse power. Offerings commonly start around 1/2 HP and can go up to 7 HP models. As motor size increases, you’ll see higher and broader spray patterns.
For example, in the table below, you can see the relative pattern size increase when a larger horsepower motor is used. The pattern here is the Linden design from the Kasco JF series fountains.
HP | Pattern Height | Pattern Width |
3/4 | 9 feet | 29 Feet |
1 | 12 feet | 31 feet |
2 | 15.5 feet | 38 feet |
3 | 20.5 feet | 38 feet |
5 | 24.5 feet | 46 feet |
7.5 | 26 feet | 46 feet |
Many people prefer fountains because they do provide a very attractive and appealing aspect to a pond. The sound of the droplets of water landing back in the pond can be relaxing and the spray patterns today are varied and attractive.
Light kits can also be added to fountains and that really enhances their display at night. Recent advancements in LED technology now allow for very efficient lighting as well as color changing features at the touch of a button.
As far as aeration capability is concerned, a fountain will help increase oxygen into the pond, much in the same way that rainfall would. Oxygen enters a pond environment at it’s surface…and anytime something reduces or breaks the water’s surface tension you will see oxygen transfer from the atmosphere into the pond. Robust wave action on windy days can help for the same reason.
When a fountain spray re-enters the water, it too will increase the intake of oxygen into the water from the air above. Under the surface, the fountain is also pulling water from around and below it, so there is an improved circulatory affect as well. The ongoing operation of the fountain will help to increase and maintain good oxygen levels through this process.
As a general rule, most fountain manufacturers will suggest around 1 HP per surface acre when fitting a fountain to a pond or lake for aeration purposes. Spray size and pattern preferences may also play into sizing the fountain and most people are looking for a balance between adding aeration to the pond and creating an eye-pleasing display.
Surface Aerators
Another, albeit less attractive, but very functional device, that you might see floating around is a type of pond bubbler or surface based aerator. The purpose of these is not geared as much towards aesthetics, but more for functionality. They move a lot of water and provide an increased degree of circulation and high oxygenation into the water.
Surface aerators create a very high oxygen transfer into the pond. This is why fish farms use them. In these settings fish stocking rates are extremely high. The ponds are normally fairly shallow, and of course growth rates are of paramount importance.
The same could be said for waste water or industrial facilities. In these cases, a surface aerator may be used to help settle out particulates, waste material, or discharge gases from the water. These are not typical things that most pond owners would need to worry about, but for places that require such work, a surface aerator can be very helpful.
On a side note, despite the fact that they don’t look quite the same as a high spraying fountain, I have found the larger horsepower surface aerators to look rather nice with display lighting.
Sub-Surface Pond Aerators
Sub-Surface aerators are simple in design and function. They use a land-based compressor or pump that’s connected to an airline. This airline runs from the pump to a diffuser that sits at the bottom of the pond. The diffuser design may come in some unique configurations but all of them use very fine holes that are punched in a rubber membrane, and air is driven out through these holes and into the water.
A very fine array of bubbles are released in a column that rises up to the surface of the pond and this diffused air, as you might guess, breaks the surface tension of the water from below. And just like a fountain, it aids in the process of oxygen entering the pond.
An aerator also creates a bit of a rotational circulation which goes up to the surface, along the surface horizontally, and then back down and across the bottom of the pond. In this way, a sub-surface aerator can provide excellent mixing of the entire pond body and increase dissolved oxygen levels from top to bottom as well.
Aeration kits can be adapted to fit most any size of pond and larger compressors and multiple diffusers are common in very large ponds that are over an acre in size.
In addition, with this type of aerator and the efficiency of the pump, there is the option to use solar power for daytime operation, or full time solar aeration with a battery back up.
Why Pond Depth, Size, And More, Matter
Which brings us to the question of what ponds will benefit from any of these systems. In truth, any pond will benefit from some increase of circulation and aeration however there are two primary considerations that will determine what type of aeration will work best.
Depth is probably the number one determining factor in which system will work the best for a particular pond.
If a fountain is your kit of choice, a shallow pond will actually benefit more from these. Because they are at the surface and draw water from a few feet down, most of the circulation and all of the aeration occurs at and near the surface itself. If the pond is much over six to eight feet deep, one can still find low oxygen levels in deeper ponds.
Typically when aerating you want to try to positively affect as much of the pond as possible. One caveat to that, and the one case where we often use a surface based aerator or fountain, even with deep ponds, involves raising trout.
Aerating For Trout
Trout require very cool to cold water to do well…and they are very sensitive to many things, including water temperatures. Fortunately we can balance their need for good oxygen levels and cool water by only aerating the upper part of a deep pond. This way they can come up to the higher oxygen areas when they need to, or go deeper for cooler conditions if they’d prefer that.
Getting back to working in a shallow pond of 6′ or less. A fountain would work here most certainly, but there are bottom based, diffused aeration systems that are designed to work in depths of six feet or less. For pond owners wanting to maximize the aeration benefits, while maintaining a more natural appearance at the surface, this would make a good choice. Sub-surface aerators can be very covert in their appearance, but they do a lot of good work under the water.
Depth Increases And Bottom Aeration
As depth increases to anything over 8 to 10 feet sub-surface aeration systems become more and more attractive.
While it’s true that they don’t help much with the look of a pond like a fountain would, they can actually keep them cleaner and healthier because they assist in increasing dissolved oxygen in deep areas of a pond or lake. It’s these spots where oxygen is inherently low and if it is, aerobic bacteria, which helps to clean up organic elements in the pond, will be hindered quite a bit.
So, in a round about way, submerged aeration can actually help to keep problems like algae blooms in check which in turn greatly improves the appearance of the pond itself.
It’s also quite possible to use both systems together if the need should call for it. Normally you would see this in a very deep and large body of water that can benefit greatly from bottom aeration and where the owner may still want the look of a fountain at the surface. The two systems integrate just fine with one another.
Fountains Versus Aerators – A Direct Comparison
As we wrap up this discussion on fountains and aerators let’s look at how they stand up against one another in comparisons.
First of all, when it comes to costs, in most cases a comparable sub-surface aerator will be less expensive than a fountain. This isn’t always the case but usually you’ll find a difference of several hundred dollars if not more.
The table below lists the price comparison between the Kasco JF series of fountains and the Kasco Robust-Aire sub-surface systems. The fountains are priced with the option of a 100′ power cable (longer cable lengths are available).
The RA systems are priced with the stock or standard airline configurations. For the RA1 to RA3, 100′ of weighted airline is allocated per diffuser, so the RA1 has 100′ included, and the RA3 as 300′ included. Extra airline can be purchased to add to the system. In the case of the RA4 to RA6, this price does not included airline which allows for more flexibility in setting up the system. You only purchase what you may need.
A protective cabinet may also add to this cost should you need one…the prices listed here are for the base model, no cabinet versions.
All of the devices priced here are wired for 115 volts, while 230 volt is optional. Prices do increase on the fountains with higher voltage wiring.
The prices as shown are current at the time of this writing (fall 2021) but may have changed by the time you read this. It’s recommended to check online for the latest pricing updates from Kasco.
Fountain / HP | Pond Size | Purchase Price -100' Cable |
3400JF / 3/4 HP | 3/4 Acre | $1721.00 |
4400JF / 1 HP | 1 Acre | $2309.00 |
8400JF / 2 HP | 2 Acres | $5178.00 |
3.1JF / 3 HP | 3 Acres | $5831.00 |
5.1JF / 5 HP | 5 Acres | $6544.00 |
Sub-Surface - HP | Pond Size | Purchase Price As Stocked |
RA1 / 1/4 HP | Up to 1 Acre | $1130.00 |
RA2 / 1/4 HP | 2 Acres | $1671.00 |
RA3 / 1/2 HP | 3 Acres | $2172.00 |
RA4 / 2 x 1/4 HP | 4 Acres | $3342.00 |
RA5 / 1/4 & 1/2 HP | 5 Acres | $3843.00 |
RA6 / 2 x 1/2 HP | 6 Acres | $4344.00 |
Fountains are more prone to plugging up since they pull water into them from down below. If there is a lot of plant growth or debris in the water, this can get pulled into the intake and the fountain output will be affected. We’ve even found masses of tadpoles in one unit when they hatched out one summer.
Aerators on the other hand use a land based pump to push air into the water so they tend to be more trouble free. Diffuser heads can get covered with muck if they aren’t run for a time but usually since air is being pushed out of them, they stay clean throughout the season.
Operational costs may vary a good bit as well because many fountains use larger horsepower pumps compared to an aerator. This makes sense because the fountain drives water, while the aerator pushes air, and this can lead to more cost to run them.
Fountain / HP | Pond Size | Daily Cost - 24 Hrs | Monthly Cost 24/7 |
3400JF / 3/4 HP | 3/4 Acre | $1.78 | $53.40 |
4400JF / 1 HP | 1 Acre | $3.01 | $90.30 |
8400JF / 2 HP | 2 Acres | $5.47 | $164.10 |
3.1JF / 3 HP | 3 Acres | $7.33 | $219.90 |
5.1JF / 5 HP | 5 Acres | $10.94 | $328.20 |
Sub-Surface - HP | Pond Size | Daily Cost - 24 Hrs | Monthly Cost 24/7 |
RA1 / 1/4 HP | Up to 1 Acre | $0.72 | $21.60 |
RA2 / 1/4 HP | 2 Acres | $0.72 | $21.60 |
RA3 / 1/2 HP | 3 Acres | $1.01 | $30.30 |
RA4 / 2 x 1/4 HP | 4 Acres | $1.47 | $44.10 |
RA5 / 1/4 & 1/2 HP | 5 Acres | $1.79 | $53.70 |
RA6 / 2 x 1/2 HP | 6 Acres | $2.02 | $60.60 |
Most people that have fountains, don’t tend to operate them 24/7. Many are placed on timers to keep daily operational costs down, along with the wear and tear on the fountain itself. Ideally though it’s best to aerate as much as possible and this is where the economy of the sub-surface system is of great benefit. The aerator compressors are designed for full time operation and even some very capable pumps cost less than a dollar a day to run 24/7.
For very large bodies of water it’s very likely that your sub-surface aeration system will need to use multiple diffusers. These should be spread out evenly through the pond area. A good rule of thumb might be about one diffuser per surface acre of water, however if a pond is shallow, it will take more diffusers to cover the same area. In other words you lose coverage range as you lose depth.
Installation for both systems is relatively straightforward and simple so they are similar in that regard.
A fountain or surface aerator is simply towed into place and moored with land lines, and the power line is run to shore and plugged into the control box there. Cable lengths will vary of course so you’ll want to consider where you intend to place the fountain in the pond, and how far that might be to your power source. Fountains can be set up to run off 115 volts or 230 volts (large fountains may go higher) and you might save a bit of money in operation with the 230v option…especially as the horsepower increases on the motor.
For the sub-surface aerator, the pump and protective cabinet would be placed near the power source and airline is the connection between the pump and diffuser(s). Once connected, the diffuser can be taken out in a boat and simply lowered down to the bottom of the pond. Be sure to check out this article with more details on how to install a pond aerator.
Also be sure to visit a recent article that we posted that can help you get a better idea on what size of aerator would work in your pond.
Maintenance Of A Fountain vs An Aerator
Last but not least, we need to talk about maintenance. There is no doubt that fountains and aerators are uniquely different devices. Fortunately though the maintenance on each is pretty straightforward.
Fountains will generally require more routine cleaning. Keeping the intake screen free of debris and build up is important. On some fountains a zinc anode is included to help guard against corrosion, and most motor assemblies are sealed. These require very little maintenance on a regular basis, but every handful of years it’s not a bad idea to have the seals updated and the oil changed out to provide a longer running life of the motor. This would typically be done by the manufacturer or one of their authorized service centers.
For a sub-surface aeration compressor, there are two points of maintenance. The intake air filter needs to be changed as required…the time frame could vary based on how dirty or dusty the air is around the pump. Some can go up to a year without a new filter while others should be changed every few months.
After several years of operation, there will be some wear down on the piston seals and these should be updated to avoid compression loss. All manufacturers provide kits to update the up and the process is relatively simple and can be done in about a half hour on site.
Fountain Or Aerator – What Will Work Better For You?
Let’s cut to the chase and get down to why you probably came here in the first place. Which type of aeration is going to work best for you? Although it’s not a cut and dried answer…there are variables and preferences than need to be considered too. Such as how you want the pond to look. Do you want a decorative fountain display, or a lighted feature at night, or nothing on the surface at all? Only you can answer that for yourself. However I can suggest, what I would do if my main focus was simply purposeful aeration.
In terms of outright aeration quality, meaning that the result of adding some form of aeration is going to increase the circulation and mixing of the pond water, and increase the dissolved oxygen levels in the pond…my suggestion is to consider a fountain, surface aerator, or a diffused shallow aeration kit, if you have a pond that’s less than 6 to 8 feet in depth.
If your pond is much deeper than this, I’d suggest that you shift your research to a sub-surface type aerator that will provide more benefits in deeper water.
In making these considerations, you’ll be getting the most out of your investment, keeping operational costs as reasonable as possible, and improving the chances of getting better, widespread results in your pond.
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