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Today’s question comes from John in Indianapolis. He writes, “I have a 1/2 acre pond with no aeration, but I want to add some to help my fish. What size of pond aerator do I need?
Thanks for the question John!
Sizing a pond aerator to a pond or lake is a pretty straightforward process. Most pond aeration systems are tested or analyzed by the manufacturers for their ability to mix and oxygenate a certain volume of water in a set period of time. Usually every 24 hours. The surface area of the pond is a consideration of course, but the depth (both max and average) of the pond, is a greater determinant of an aerators coverage. In essence, the deeper you place a diffuser in a pond, the more pond area it will affect. You can use this knowledge to easily choose the right pond aerator for your particular pond.
Pond Size And Depth Are Used To Choose The Right Aerator
Here’s an example. If I were to put a diffuser at 6′ of depth I may be able to effectively aerate about a 1/4 of pond area…and that’s probably being generous. The same diffuser, placed at 12 to 15 feet, will aerate up to an acre and provide excellent mixing and oxygenation.
So for sizing purposes, depth, along with a surface area estimation are both critical considerations.
In regards to your question John, since depth wasn’t mentioned, it will be harder to really pin down the exact aerator to use here but I can give you a few suggestions and examples that I think will help.
Types Of Pond Aerators To Consider
Large pond aerators, at least as far as the current market and offerings are concerned, can be broken down into a few categories. First of all, in this article, it should be noted that we are focusing on the sub-surface, diffused aeration systems. In this category, there are shallow pond systems, most of which are designed to work in ponds of 6′ or less, and standard or more deep water systems that are rated down to 50′ of depth. I do try to maintain a bit of a buffer off that max depth however and prefer to max them out at 35 to 40 feet.
If your pond is shallow, the best system I can recommend is the Airmax SW40 which will work in ponds up to 1/2 acre. The max depth is rated at 6′ and it includes 4 diffusers and uses a linear compressor which is both efficient and quiet.
If the pond is 8′ or deeper, I would consider something like the Kasco RA1 which uses a 1/4 HP pump, and a single diffuser. If the pond is really oblong and stretched out, I may lean more to the Robust-Aire RA2, which uses the same pump but includes 2 diffusers. This helps spread the air out a bit better and mix the entire pond more effectively.
Pond Aerator Manufacturers Suggestions On Sizing
As you look over the specifications and information on the product pages, note where the manufacturer mentions coverage ranges. In the case of the RA1, Kasco notes: Effective aeration can be achieved in 1/4 acre ponds 5 to 8 feet deep, 1/2 acre ponds 8 to 12 feet deep, and 1 to 2 acre ponds 12 to 16+ feet deep. You should see this kind of thing noted by most reputable manufacturers.
Here’s another element to sizing a pond aerator to a pond or lake. As the size of the water body increases, more diffusers will be required to adequately mix and oxygenate that pond or lake. As you add diffusers to a system, usually a larger pump will be required to maintain adequate air output out of each one. We aim for no less than 1.5 cfm’s of air out of a diffuser.
In the table below I’ve listed the typical aeration systems that are used today. For simplicity, the more specialized, shallow water aerators are not included here. The 1/4, 1/2, and 3/4 horsepower pumps are are rocking piston types. The rocking piston compressor is widely used in the industry covering the broadest range of capability compared to any other type of pump. The 1 HP is a rotary vane compressor which works great on very large, multi-diffuser layouts in ponds of moderate depth.
|Pump Size||Cost – Monthly||Diffusers||Pond Size||Max Depth|
|1/4 HP||$10 to $15||1 or 2||Up to 2 acres||50′|
|1/2 HP||$24 to $27||2 or 3||Up to 3.5 acres||50′|
|3/4 HP||$32 to $40||4||Up to 4.5 acres||50′|
|1 HP||$55 to $65||6||Up to 8 acres||18′|
You will see some overlap here in the number of diffusers powered by a particular pump. The 1/4 HP compressor can effectively work with up to 2 diffusers but not more. The 1/2 HP is very commonly used in 3 diffuser systems, but can be very good at powering two diffusers as well. We might use this combination in deeper ponds of 25′ or more. It should not be used with one diffuser (which may create excess back pressure on the pump), nor would I routinely use it with four diffusers in a typical aeration system, although it could be used with four diffusers in some shallow water ponds that are less than 10′.
When Pond Aeration Mapping Is Useful
On larger waters, these airline runs are best estimated using Google Earth, by laying out an aerial mapping. It’s easy to do, and will provide the details needed to fit a good aeration system to even the largest ponds and lakes.
To map a pond or lake, three pieces of information are needed. Normally I’ll ask for the address or location so I can find the body of water on Google Earth. Second, we want to discuss the pond depths, both average and max and get a feel for that data. And finally we would note where power might be located around the pond, or somewhere nearby.
With that information a mapping tech can get to work and prepare a report that outlines what aeration system is recommended and how much airline and components will be required to complete the set up. Using this a quote can be provided to break down the total cost of the pond aeration system.
I normally don’t need to map out ponds smaller than an acre or two as those are pretty straightforward in the set up, but as size increases, it makes more sense to lay everything out on paper.
Sizing a pond aerator properly to a body of water is, in a sense, a bit of an art, and a bit of science. We can take the data and specs from the makers of such systems, and use that as a guide in fitting their particular aerators to a pond. Along with that, technology like satellite imagery makes the work easier too. And finally, some good, old fashioned common sense, plays a part as well. Once you recognize the relationship between surface size and depth, and the role the latter plays in aeration coverage, you’ll be better equipped to find the right sized aerator for your pond.
As always, if you have questions on pond aerator, or anything pond related for that matter, be sure to send them in…I’ll make a point to try to feature them here on the Pond Q & A Of The Day.
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