Pond Boss Forums AERATION Should I aerate? Aeration, muck, and thermal refuge

Hi all,

We have got a relatively new pond located in Eastern Kansas that has SMB, walleye, and yellow perch. Really am hoping to prevent muck accumulation and vegetation overgrowth particularly in the swimming area around the dock. The lake is clear and very harboring for submerged vegetation that is getting out of hand. The lake is about 6 acres and 18 feet deep. Was hoping to treat the vegetation next year and keep it in check as much as possible in the swimming area but am concerned with all the dead organics and the eventual buildup of muck in that area and also throughout the whole lake.

Would best practice hear be to treat the swimming area, physically remove the dead plant material, and keep an eye on regrowth throughout the season?

Would diffused aeration, beneficial bacteria, and some form of biologic control for trimming/controlling (grass carp) be the best way to manage the rest of the lake and limit overgrowth and muck accumulation? Just curious about the best preventative strategies here and if diffused aeration/microbe treatments would even be a necessary investment at this point.

My last concern and confusion is regarding diffused aeration and thermal refuge. I don't want to completely eliminate the thermal refuge for these colder water species but when you aerate just part of a pond are you not just constantly pushing anoxic water up? Can aeration be beneficial if you don't aerate/mix the entire lake? I have seen people just throw aerators and beneficial bacteria treatments in shallow targeted areas or coves (especially in more eutrophic ponds) and want to understand that.

Any help is greatly appreciated!

Welcome to Pond Boss!

Lots of semi-complicated questions in your post above.

Yes, the plant materials in your lake will generate a small amount of organic "muck" on the bottom of your pond. IMO, it is far important to keep all of the OTHER organic debris out of your pond.

What is the water source for your lake? Is it a small, seasonal creek? Is it just surface water runoff from the watershed above the pond? The organics from those sources are far easier to control than the ones that actually exist within the life cycle inside your pond. Keep all of those leaves, pine needles, grass cuttings, etc. out of your pond.

The other thing to exclude from your pond are "fertilizers", either natural or man-made. Are there any fertilized agricultural fields in your watershed? Any livestock animals?

You also need to identify the submerged vegetation that is getting out of hand. Read some of the posts in the identifying plants sub-forum. If you can't identify your plant, then you will learn how to send proper pictures to Pond Boss to aid in the identification. One you know the exact plant types, there are plenty of experts on the forum that can help with your control/eradication.

Another option is to plant some beneficial plants to take up some of the fertilizer in your pond and deny it to the undesirable plants. There are some types of submerged plants, and some emergent shoreline plants good for that duty.

Pond dyes may also be beneficial in retarding the growth of submerged nuisance plants and filamentous algae.


As regards your aeration questions - there are multiple experts on that topic in the forum that can help you with that.

You are correct the aeration brings up anoxic water from the bottom of the pond into the zone where your fish are living. However, that is only true at the startup of aeration. That is why you start your system using baby steps.

You can put the aeration diffusers on stands to keep them off of the bottom. The concept of a thermal refuge at the bottom of the pond does sound attractive for "cold water" species such as you have stocked. However, in practice the fish will not go into the cooler but anoxic water at the bottom of the pond during peak summer. They will prefer slightly warmer, but well oxygenated water.

In addition to keeping your fish happy, the aerators will serve the dual purpose of keeping some of the fine organic debris suspended in the aerated water column. This will allow aerobic bacteria to break down the organic material. This should serve to significantly reduce your muck accumulation rate on the bottom of your pond.

Off topic: I like the fish species in your new pond, but you do not appear to have any species that will provide long-term forage for your fish at the top of the food chain. Did you just list your predator fish? If not, you may need to start a new thread about balance for your pond, otherwise your main species may experience very slow growth.

Congratulations on your new pond!

If you have an issue with plants the first step is to ID them, then you can find the exact method to suppress them.

As to what you should do with the remains---the thing to remember is that plants are made from water and CO2. A lot of people imagine trees are made from dirt, but that's not the case. Everything other than water and CO2 is minute.

Making plants produces a lot of oxygen---decomposing them requires a lot also. But water doesn't hold much oxygen, So (TLDR) natural processes are not good at removing muck. A pitchfork however...

The water shed is just a field in CRP mainly fescue. There is another pond way upstream that I know can run but it very very limited. No agricultural runoff or fertilizer going in but the grass is mowed and grass clippings will enter the pond from time to time. Should have noted this but American pond weed, bushy pond weed, and filamentous algae are what I have seen. I am not so much concerned with the actual plant growth as I believe I can handle that and control it but more so the muck accumulation piece and my concern about the cold water fish species and aeration. I believe the colder water species like walleye will seek that thermal refuge and more adequate temp ranges until the O2 levels become lethal, in other words, they will sit in that thermocline. But if I aerate the pond and do sort of what you are saying with the stands for the aerators I can maintain a thermocline and aerate the pond bottom in areas where organics are piling up the most like along the edges? I guess I was worried that if I didn't aerate the whole thing top to bottom I would pull up some water below the thermocline and mix it which could cause issues but maybe that doesn't make sense as that water would be the most dense and sit below the aerators.

Yes, with aerators on stands you will keep most of the pond bottom above the stand elevation in an aerated water condition. This will help retard organic muck accumulation. However, this will also help slightly with muck accumulation in the center of the pond where the water is deeper than your stands.

A heavy, water-logged oak leaf will definitely settle to the bottom of the pond outside of your aeration lift columns. However, there is usually a fair amount of tiny bits of SUSPENDED organic material in the water column. Some of that material may be in the deep center of your pond and outside or your aeration circulation cells. However, if you have two days of big winds at the pond, then the center water is going to get pushed over to some of your aerators. They will then keep that material in the aerated water column for some extra time, and allow the aerobic bacteria to work on your material that otherwise would have become bottom muck.

Aeration diffusers off of the bottom is not a perfect solution, but it will give you multiple big benefits to your pond. The biggest of course being aerated water for your fish.

One reason "cold water" fish thrive better in colder water is that they are more likely to perish during an oxygen crash event than many warmer water fish. Warm water holds significantly less dissolved oxygen.

I believe walleye and yellow perch are more likely to avoid an August high temperature fish kill in an aerated pond compared to an un-aerated pond that is located a bit farther north - even though the latter would have been naturally cooler. (If this is wrong, experts please correct or clarify!) I think that is a very important consideration for the benefits of aeration in your pond, especially based on your geographic location at the southern edge of where your fish generally thrive.

You are also correct about the aeration bringing up lots of anoxic water into the level where your fish are living. However, that only applies to the INITIAL conditions in a strongly stratified pond at the start of aeration. There is a very comprehensive set of guidelines to be followed whenever you start aeration from a previously stratified condition. Several of our aeration experts have outlined those rules in some of the other threads.

I firmly believe that having a well aerated pond outweighs the downside of having warmer water at the bottom of the pond. Without testing equipment you won't be able to check your O2 levels, but here is some first hand information.

Trout are not supposed to survive in ponds that get warmer than 70°F. OR survive in water that has less than 5mg/l O2 for long periods of time. A customer that had both a bottom diffusion aeration system and a surface agitator type aerator had trout survive into the low to mid 80°F water temp range (mid 80's at the surface, low 80's at the bottom) due to the amount of O2 that the water was carrying. It was at saturation level top to bottom, which was above what the trout needed to survive.

Since both WE and YP need much less O2 than trout to survive, I think that you will be just fine with the air stations set on the bottom of the pond providing that the system is designed correctly for the pond and the air stations are placed correctly in the pond. Like FR said above, having the air stations placed correctly in the pond eliminates the dead space between the aeration cones of influence in the pond.

Once the system is set up and running for a week, you will not have any anoxic water at the bottom of the pond.

Thank you for the replies!

That is such an interesting case study in regards to the trout

Planning to map the pond to do a custom system if that would be the best route to be sure design/placement is adequate

Would you recommend utilizing any of the beneficial microbial treatments or muck reduction products yet? Just want to stay ahead of things

I am not sure whether the muck reducing products are worth the squeeze if the pond has a properly designed aeration system in it and it is run according to its design. Meaning if the system is designed to be run 24/7 and you only run it at night you might not see the amount of O2 at the bottom of the pond where the bacteria will be working on the organics that you would see if you ran it 24/7.Aerobic bacteria break down organics much faster than anaerobic bacteria.

That's the reason why aeration systems are used in waste water treatment plants.

Septic aerators move orders of mag more air and water (proportionally).

I'd really like to see the math on how much O2 it takes to break down muck vs how much is available with aeration vs without.

I figure most of the dissolved oxygen added to the pond by aeration comes from spreading the O2 that's naturally produced in shallow water during the day to deeper water that's able to absorb it, instead of it rising up and outgassing into the atmosphere where 99% of the O2 produced by the pond during the day ends up. The amount that's directly added by bubblers is minute.

Thus you'd think it'd be better to run the aerators during the day than at night. I mean, I'd think. But I really have no idea.

Unless you have an O2 meter and check the level of O2 in the pond water, you are correct, you are just guessing. What data have you seen that makes you think that the pond outgasses O2 into the atmosphere? What data has shown that it is better to run the aeration system during the day vs the night? You said that septic aerators move order of magnitude more air and water than pond aerators. How many GPH of water will a typical septic aeration system move per hp?

While it may not seem to be much of a change in a 1 acre pond, 5.2 mg/l changed to 6.9mg/l overnight when a 1/4 hp pond aeration system was started up after sundown and was run all night. That particular system moved roughly 400,000 gpm of water to the surface.

Just a back of the napkin calculation without the napkin. Dissolved oxygen is measured in milligrams per liter and the saturation points are very low esp at summer temperatures. Meanwhile an acre of algae is producing way more O2 than the surface water can hold. It's got to go somewhere and (unfortunately) it ain't sinking into the depths.

Re: the aerator I assume you mean gallons per hour or gallons per day, but how much is the water's surface area actually increased? Probably not very much. That's where the picking up atmospheric O2 happens. If the water all has the same DO concentration moving it around won't increase the rate it's absorbed from the atmosphere. Like I said I'd guess it wasn't adding much O2 to the pond water overall, just redistributing what was already dissolved in the water. But I'm not any kind of expert and reality often doesn't conform with what you'd expect.

Firstly,,, scientific literature and my college limnology education has proven that a majority (a big majority) of the DO in the ocean and freshwater is produced by phytoplankton, periphyton, and submerged macophytes i.e. phothsynthesis. Look it up. Surface DO diffusion from the atmosphere does add DO, but it is not nealy as much compared to the photosynthesis processes. Ask AI to get an education.

Rarely does Photosynthesis produce enough DO (supersaturated) that the DO gets degassed by diffusing to the atmosphore. It happens but not frequently and it is especially rare in the open water the pelagic areas. Supersaturation happens most frequently in shallow littoral zones with lots of submerged macrophytes or algae and minimal circulation currents. See postscript,

Secondly, I have dealt with mechanical aeration for 40 years. Aerating 6 acres of water is a big expense. I have never seen good research proof, just speculation that benthic aeration on just one area such as the swimming area (0.5 to 1 acre) proves to be a big detriment to the ecology of the pond. Zonal aeration does not and will not mix the entire 6 acre pond but IMO a well designed unit could mix one end or region (1 - 2 acre) of the pond to circulate water bottom to top in the area of mixing influence to aid the organics decomposition that is of main concern.

Thirdly, my testing has proven placing diffusers on stands up off the bottom (2-3ft) does not during summer mix or send water below the height of the diffuser head. Diffuser use during winter (water 39-40F) can mix water below the diffuser head. Test it and prove me wrong. Thus diffusers on stands during summer develop deeper sludge layers that other areas of the pond with diffusers close to or lying directly on the bottom. My aeration diffuers proved this concept during the last 20 years. I confirmed that in 2025.

As you, kansasbass, mention, I would map with depth profiles the pond and focus on the region of the end with the swimming area.

I think in theory you could mechanically well mix aerate the 1 - 2 acres of the swimming zone and you should be able to get adequate DO on the bottom for good or better decomposition of the accumulated organics in the swimming part of the pond. Be prepared to be able to test the depths of the sediments. There is a tool called Sludge Judge. This regional method of aeration could be or should be a very good test case study. However for knowing the results of regional aeration, you would have to buy a decent or dependable good qualityl DO meter. They are not cheap but worth the money to monitor DO in all areas in the small lake, large pond if monitoring quality quality is important for goals of your 6 ac lake. Remote areas from the diffusers will likely remain stratified and/or have anoxic (no DO) conditons. Good DO testing will show the concentraions of DO at any depth.

Also you should buy or make a Secchi disk and regularly measure the water clarity. Water cleaity measurements using a Secchi will tell you how deep of water the natural oxygen is being produced. Learn about euphotic zone and application of Secchi disk.

Postscript
AI - Oxygen gas bubble disease, also known as gas bubble disease (GBD), occurs when aquatic organisms like fish are exposed to water supersaturated with gases, leading to gas bubbles forming in their blood and tissues. This can be caused by faulty equipment, human error, or natural events, and it can lead to symptoms such as visible bubbles under the skin, eye bulging, buoyancy problems, lethargy, and even death.

GPH is gallons per hour. mg/L is milligrams per liter.

In my real world example in my previous post above, that is how many gallons of water per hour is brought up to the surface to interact with the O2 that is in the atmosphere. Water doesn't have the same O2 levels in it when it's not moving due to aeration - the lower in the water column the O2 reading is taken, the lower the O2 concentration is. The only time that I have not seen that happen is in crystal clear water that had FA growing down on the bottom of the pond in 14' of water. That was temporary, as the water warmed up a few weeks later, a phytoplankton bloom started, and visibility diminished, killing the algae in the deeper water and the O2 levels there plummeted.

Water that has a bottom diffusion aeration system in it gets the majority of O2 transfer to it from it interacting with the atmospheric air, NOT the air that is pumped into the diffuser(s) in the pond.

Using an optical O2 meter I have never seen calm water in a pond that was not aerated or mechanically agitated at 100% O2 saturation levels, no mater what the water temperature. I HAVE seen water at saturation levels at the surface when the pond had both bottom diffusion aeration and surface agitation systems running at the same time.

When you say "an acre of algae is producing way more O2 than the surface water can hold", please define the thickness of the algae (wet weight density of algae in kg/gallon) and the thickness of the surface water that you are referring to. Are you referring to an O2 production system or algae in a pond? I am asking these questions because I cannot agree or disagree with statements that are not quantified.

In a production O2 generating system where algae is used to produce O2, 5 kg to 10 kg of wet algae will produce between 55g to 83g of O2 per hour in optimum conditions. In a pond, when sunlight no longer reaches the algae in the pond, it stops producing O2 and starts consuming O2, at the detriment to the fish that are in the pond. 5 kg to 10 kg of wet algae will need to consume between 10g to 600g of O2 per hour that it is without sunlight.

I don't do well with theoretical calculations, but I can do them when required. I prefer to go out on the water and measure. There are way too many variables in real life. That's why I have a YSI Pro ODO meter.

In ponds, theory diverges from what actually is happening in the pond very quickly. Surface water mixes with non-surface water pretty quickly. Dump a quart or two of dye in a pond and see how fast the whole pond changes color when the pond does not have an aeration system or fountain in it. If there is a thermocline in the pond, the dye will not mix into the lower water depths as fast as it mixes with the upper water column. (below the thermocline vs above the thermocline)

So, circling back to your statement that "I figure most of the dissolved oxygen added to the pond by aeration comes from spreading the O2 that's naturally produced in shallow water during the day to deeper water that's able to absorb it, instead of it rising up and outgassing into the atmosphere where 99% of the O2 produced by the pond during the day ends up. The amount that's directly added by bubblers is minute.", I have to strongly disagree.

That is why in real life that pond owners that have no bottom diffusion or surface agitation aeration systems in their ponds AND have a secchi disk reading of <12" due to an algal bloom have a very good chance of having a summer kill at night during the summer due to O2 levels in the pond dropping below the levels that are required by fish to survive.

In a HOA customers 18 acre non-aerated pond, they were experiencing both summer and winter fish kills. Secchi disk readings were anywhere from 8" to 16" during the summer, due to phytoplankton blooms. Their budget could not support installing a bottom diffusion aeration system in the whole pond that 1st year, so we only installed a system in the North half of the pond that ran 24/7. That August, the half of the pond that did NOT have an aeration system in it experienced a summer kill while the other half of the pond did not. Wind was from the South, and 2-3 days later the dead fish floated to the North side of the pond. If I wasn't there the day after the fish kill event to observe where the dead fish were before the wind moved them around, I wouldn't have known that and would have assumed that the fish died all over the pond instead of the half of the pond without aeration.

Just want to add a little additional context. The oxygen cycle where it comes to plants isn't always just a net positive of oxygen. For there to be a net positive contribution to DO, the plants need to be increasing in weight. This sequestration of CO2 results in net positive contribution of O2 but one cannot depend entirely on plants for O2. They usually reach a limiting weight and then the net is zero. If the standing weight of living plants declines, this can result in a net negative production of O2 because of the oxygen demand of decomposition of the dead plant material. But it does depend on the rate of decomposition the dead plants. Where muck is accumulating in O2 depleted water, the rate of consumption is often less than the production of O2 by living and growing plants that remain. Essentially, this is how the Earth itself became oxygenated. Dead materials were prevented from decaying and that is how the Earth accumulated O2. Still, DO diffuses to the bottom and so DO from upper layers is slowly consumed by decomposition taking on the pond bottom. The evidence of the diffusion is the gradient of DO that is observed where DO is lowest at the pond bottom.

There is a daily cycle of O2 that plants directly cause. During the day, plants accumulate photosynthesized sugars which contained energy is used to fuel metabolism and growth. Metabolism and growth continue in the dark and during this time oxygen is used by the plants to extract energy from the sugar. They consume oxygen they produced during daylight at night. But so long as there is net gain in the energy contained of the standing weight of plants, there is a net contribution of O2 by plants over the course of the entire day.

Absorption of atmospheric oxygen is important to DO. Aeration enhances absorption by bringing depleted water to the surface (whose affinity for absorption is greater than saturated water) and by disturbing the surface tension (something that elevates the time rate of absorption. Atmospheric oxygen is essential to the health of water and its inhabitants. Plants in the water will not be sufficient to produce the needed DO all the time ... though they may be part of the time.

Generally, water with high nutrients and high standing weights of plants have higher oxygen demand and more problems with DO. The more plants one has (whether blooms of phytoplankton or vascular plants) the greater the need for efficient absorption of atmospheric O2. The greater the need for aeration. Aeration will accelerate decomposition of organics that accumulate on the pond bottom. In as much as that is true, aeration increases the demand for O2 ... but this is supplied by the aeration itself where the source is atmospheric oxygen.