Pond Boss Forums INTRO Questions & Observations Pond Areation

I have a 3 acre pond that is 18’ deep. The depth drops off pretty quick from the sides. It is long with depths at the shallow end at 5’. At what depth should I set my diffusers?

Normally the diffusers are set in the deepest basin/s of the pond. IMO your goal for pond mixing is to daily lift all the water out of the deep basin to the surface. Bottom water near the bottom loses the DO (dissolved oxygen) first thus you want to get that low DO water up and out of the deepest zone of the pond. Water clarity has a big influence as to how deep in the pond that DO is being naturally produced. Thus it is more important to run the aerator longer when the water clarity of the pond is reduced as in 2-3ft visibility. AERATOR RUN TIMES ARE BASED ON HOW MUCH WATER ALL THE DIFFUSERS LIFT TO THE SURFACE PER HOUR AND HOW MANY GALLONS OF WATER THERE ARE IN THE POND.

Thanks for your response. I have them set in the deeper parts of the pond now and running them 24/7. It was suggested to me by a fish hatchery owner, to not run them in the deepest parts but in my case in about 10-12’ of water. They said the diffusers work more efficiently at shallower depths. I have also read not to run them in deep water in the winter, so as to not disturb the warm temperatures. I live in SE Iowa. I think I will move them to shallower water in the winter. I am open to any advice. What I am learning is there are about as many opinions as there are Ponds.

I don't know who made your diffusers. Here is a chart from Vertex. As you can see, the diffusers work more efficiently in deeper water than shallow water. Now the deeper the water is where the diffusers are placed? The less air the compressor spits out. But I agree with Bill, put them in the deepest part of the pond.

When we calculate an aeration system for a pond, we like to see more than 1x water volume lift rate/day. That allows for decreased lift rate as the system ages or the diffusers get covered with bio-film and don't work as efficiently.

Now for the winter, what we do is run another airstation (diffuser) in 1/4 to a max of 1/3 total pond depth, and within roughly 20 feet of shore. That one runs in the winter to keep an open hole and the ones in the deepest part of the pond are shut off. No messing around when it's cold out with wet, muddy, self-sink airlines. We shoot for an open water area that is 1% of the total pond surface. If it is a bigger pond, then we run enough airstations to get that number.

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Aeration water volume mixing chart presented by esshup has valuable information as it was produced by actual testing. Note the lifting rate is in gallons per minute; then X 60 for gallons per hour. As you can see from the chart diffusers move MORE water when placed deeper. It makes no ecological sense to me to put diffuser water lifter circulators in water in 10ft -12ft deep when the pond is 18ft deep unless there is a special situations, which are rare.

Then when diffusers are at 10ft-12 ft deep this results in water deeper than 12 ft developing no oxygen (DO) and the sediments become anoxic (aka anaerobic). In this condition,,, black sediments are created, hydrogen sulfide and methane gasses are created and pH is reduced and various forms of decomposition of organic sediments are decreased 20 to 30 times; not 2 to 3 times but 20-30 times slower / less. Now how does this make sense? If someone does not believe me then just test the DO in the water below the depth of the diffuser head. Circulation of the pond water only goes as deep as the head lifting surface of the diffuser. This is due to differences in water densities. I have tested this very often and it always holds true in normal situations. Not everyone in the "pond business" is well versed fully about diffuser bottom aeration - especially when you haven't actually tested it.. "YOU DON'T KNOW WHAT YOU DON'T KNOW" via Bob Lusk.

esshup is correct - During ice cover especially with a snow cover blanket shallow diffusers can be very beneficial when operated enough to daily create an open water area so light can penetrate and naturally plants and phytoplankton make DO in the shallow open water zone. Circulations from the shallow diffusers move and mix good water for very far distances when the water is densest and very easily mixed and distributed when at 39F.

Bill is spot on. There is a reason why I have an O2 meter with a 10 meter probe. It's interesting how O2 transference in pond water is so different between summer and winter. It has to do with the density of the water. It's not necessary to run the compressor 24'7 in the winter, but I do in my pond because I tend to forget and I am sort of pushing the biochemical demand in my pond.

The reason why I said put the winter diffuser/airstation about 20 feet away from shore is because you want the ice to be melted all the way to the shoreline so anything that goes swimming can get out of the water without having to climb up on the ice.

Probably 15 years ago, I almost lost my two Springer Spaniels when they went into the water after a Canada Goose with a broken wing and a Toulouse Goose that became friends and visited my pond one year. I let them out one day to go potty and the female Springer Spaniel brought the Toulouse Goose up to the house. The following week the temp dropped and it was -12°F with a 20 mph wind. I let them out to go potty and they heard the geese in the pond again. Long story short, after thinking that I'd die in the pond if I tried getting them out of the water, I was able to break the ice with a 20' extension ladder and they swam to shore. It took them 20 minutes in a hot shower to stop shivering. After that I moved the diffuser closer to shore so that would never happen again.

If anybody wants to read more about winter aeration, order the January/February 2015 Pond Boss Magazine. There is a winter aeration article in there.

I am so glad I found this forum. You guys are a wealth of knowledge and I appreciate your help. My system is a 3/4 hp EasyPro running four diffusers. I have them running down the center, equal distances apart, in the deepest area. I will leave them there based on your suggestions, and I will run them 24/7 until it gets colder.

When do you know it is time to go to winter time operation? By the temperature of the water or air temperature? Also, same question as to when to start up in the spring?

Is there any issues to watch out for when running just one diffuser with the 3/4 hp pump?

Final questions, I have the diffusers hooked up to a 4 valve manifold that is near the pond. I have adjusted the valves so all the diffusers look like the are producing about the same about of air. If I don’t do this the deepest one doesn’t put out much air. The pressure gauge at the pump read about 10 psi. Is this normal and should I be trying to balance out the diffusers output using the valves?

I plan to buy the 2015 issue that covers winter time operations, which hopefully will answer my questions.

Thanks again for your help. I was getting a lot of conflicting information.

From all my research, only Vertex publishes these gpm lifting rates. My EasyPro diffusers "look" similar (9" EPDM disks), so I used the Vertex data in my calculations.


Yes, there is a potential problem. A single diffuser must be able to handle the air flow rate produced by the compressor. If it can't, the compressor may be damaged. Check the spec sheets of the EasyPro compressors and diffusers. That's why I purchased the 1/4 HP compressor and nothing larger for my application.


I try to balance the flow rates also. There should be about 1 psi per 2 foot of water depth. So, 10 psi sounds about right for your diffuser in 18 feet of water.

There is a way to check if there are any issues to watch out for when running just one diffuser with the 3/4 hp pump?

In addition to what Knobber posted above (Check the spec sheets of the EasyPro compressors and diffusers.) what you can do is pull out one of the diffusers from the pond . Close the other three diffuser valves while they are still in the pond. Turn on the compressor. If the compressor air gauge reads 0 operating the diffuser out of the pond the pump has no back pressure from the diffuser to the pump and the diffuser is able to freely or easily release all the air volume coming from the compressor. The reason you do not do this with just one diffuser running in the pond is because the head pressure of the water depth produces back pressure. To answer your concern,, you want the system to operate with all free air flow to see the diffuser's ability to freely release all air produced without causing any backpressure. NOTE EXCEPTION Vertex brand diffusers have a special built-in check valve that requires a small amount of pressure to open it. Very long air lines and small diameter airlines can cause some backpressure to the compressor. To avoid this concern hook up the diffuser to the pump with a short hose.

Generally most commercial membrane diffusers are able to release all the air from compressors smaller than 3/4hp; although there are some excepetions. So proceed with caution. I have seen some higher CFM compressors pop out the membrane from disk diffusers.

Bill, you are correct. I need to test the EasyPro diffuser since we are a distributor for both Vertex and EasyPro. I tested a single Vertex diffuser a number of years ago and it had no issues running for 4 months in 4' water depth during the winter when using a Gast 1023 3/4 hp rotary vane compressor. It was WAY over cfm Vertex specs. IIRC the back pressure tested like you described was 1 psi. It takes 0.5 psi to open the check valve in the Vertex diffusers.

I tell my customers that they could turn off the system when the water temp is in the low 50's and dropping and that they can turn the system back on in the Spring when it's in the upper 40's to low 50's without worrying about the start up procedure. I tell them to turn the air on going to the winter diffuser when there is or will be 2" ice and 2" snow on the pond. Some years it's on for only a week or two. Last winter it was on for about 3 months.

That is WATER Temperature, NOT air temperature. I take water temp at 12"-18" depth.

When my pond lost 9 foot of water depth due to a drought, (half the pond depth) I took out roughly 100# of fish before the pond iced over, and re-configured both the shallow and deep airstations so they'd BOTH work for the like they were supposed to. I had probably 30% of the surface area ice-free and didn't lose any fish. BUT I was concerned because of the high biochemical demand on the pond that winter.

Now what I do for my customers that have ponds that ice over, I found a diffusers that has medium sized bubbles for the winter diffuser. Larger bubbles make more surface disruption (waves) and open up a larger hole. This one uses 2-12 CFM, and has 6-10mm bubbles. Compressor specs are important, a low cfm compressor won't work with these diffusers.

If you have a pump producing too much pressure/volume for the diffusers you wish to operate at that time, you can always install a waste bleeder in the system.

At any place where you have an existing manifold, or can easily install a tee, run a short piece of hose into the air with a valve on the end. Leave that valve cracked, so that a small amount of compressed air is always wasted to the atmosphere - as opposed to operating the system above the design parameters of your diffusers.

If possible, I would place the waste bleeder at some place I travelled past frequently on my daily or weekly routines. If you hear the bleeder just screaming air, then you know you have a freeze up in your line to the diffusers. If it is not making any noise at all, then that signals several other possible problems that are nice to diagnose early.

Cody Note - Good advice as an option above. I have seen this done for several aerator systems. When you have this situation where you are releasing excess air volume, why not add another diffuser and put that wasted air to work moving water in the pond.?