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Hello everyone,

Around November of this year, we added a bottom up bubbler, 1/2HP, about 10ft from one edge of our 1 acre pond. Since then, we have had a couple weeks of cold temperatures (-16C/3.2F), but we still have very poor ice quality even on the furthers part of the pond away from the aerator. The ice is so bad that a hockey stick can go through with little force. There is still around a 20ft open section around the aerator that is slowly icing over.

I know the intention of an aerator is to leave some open water, but is there something we can do to allow for safe ice to form for fishing and skating on the other end of the pond? Is it normal for aerators to cause such bad ice quality? Other much larger lakes in our area are frozen and people are safely fishing on them.

Any advice or comments would be appreciated.

Thank you.


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Does your goal for Winter aeration require you to run it 24/7?


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Originally Posted by Theo Gallus
Does your goal for Winter aeration require you to run it 24/7?

Thanks for your reply. According to our pond manager, the goal is to leave an open area for gas exchange to promote pond health, including reducing build up of gasses to reduce weed growth after ice out. Is turning the aerator off for some period an option? I'm open to anything that allows for safe ice while also leaving a big enough opening for what was mentioned above. Thanks again.


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As there is a sufficient reserve of oxygen in our pond's water to last for days, weeks, a month or more(?), I leave our aerator off until an ice cap forms that will support our dogs and me. This could take a few days when we have very cold cold weather; it could take weeks.

I then fire up the air pump with the diffuser relatively close to shore, and in a few hours, there is an open hole. The rest of the only 1/4 acre pond remains frozen enough to support all of us. My Aussies edge up close to the open water, realizing that they could go in for an unwanted swim, but that they also can make it to shore. The dogs some times toss their tennis balls into the open water, wait back from the edge of the ice for the balls to drift in close, then stretch out and grab the floating toys. It seems like this is particularly great fun for them. Once in a while, in they go. But they happily swim to shore, shake off, and zoom back out onto the ice.

My experience has been that the ice at the edge of the hole remains rather strong.

You might try shutting down your aerator for long enough to build thick ice, then restarting it.

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Fyfer - Tell us or give us a PBoss forum link to more about some of the details of your pond. I need to know how old it is, maximum depth, water clarity, if pond dye is used and amount of dying weed growth going into late fall. Also helpful is amount of dead tree leaves that were added to the pond this fall. Water clarity of the open water is important to know. We need to estimate the biochemical oxygen demand of your pond during winter to determine the need for winter aeration. All this info provides for a good, educated, remote evaluation of how much if any that you need to be winter aerating your pond. You said "According to our pond manager, the goal is to leave an open area for gas exchange....". This is basically true for shallow, older eutrophic ponds with years of organic muck buildup. Depending on the in-depth aquatic ecological education experience and understanding of your pond manager he/she may be just giving you very generalized winter, aeration, vendor directions rather than the specific winter aeration / oxygenation needs of your pond.

Last edited by Bill Cody; 01/08/22 11:48 AM.

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Originally Posted by 4CornersPuddle
As there is a sufficient reserve of oxygen in our pond's water to last for days, weeks, a month or more(?), I leave our aerator off until an ice cap forms that will support our dogs and me. This could take a few days when we have very cold cold weather; it could take weeks.

I then fire up the air pump with the diffuser relatively close to shore, and in a few hours, there is an open hole. The rest of the only 1/4 acre pond remains frozen enough to support all of us. My Aussies edge up close to the open water, realizing that they could go in for an unwanted swim, but that they also can make it to shore. The dogs some times toss their tennis balls into the open water, wait back from the edge of the ice for the balls to drift in close, then stretch out and grab the floating toys. It seems like this is particularly great fun for them. Once in a while, in they go. But they happily swim to shore, shake off, and zoom back out onto the ice.

My experience has been that the ice at the edge of the hole remains rather strong.

You might try shutting down your aerator for long enough to build thick ice, then restarting it.


Thanks for your reply. I'm surprised the aerator can reopen the hole once it's already frozen, but that's good to know. I will determine the aeration needs and then hopefully turn of the aerator the let the ice form. We have a cold forecast so it shouldn't take long in theory. Thanks again.


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Originally Posted by Bill Cody
Fyfer - Tell us or give us a PBoss forum link to more about some of the details of your pond. I need to know how old it is, maximum depth, water clarity, if pond dye is used and amount of dying weed growth going into late fall. Also helpful is amount of dead tree leaves that were added to the pond this fall. Water clarity of the open water is important to know. We need to estimate the biochemical oxygen demand of your pond during winter to determine the need for winter aeration. All this info provides for a good, educated, remote evaluation of how much if any that you need to be winter aerating your pond. You said "According to our pond manager, the goal is to leave an open area for gas exchange....". This is basically true for shallow, older eutrophic ponds with years of organic muck buildup. Depending on the in-depth aquatic ecological education experience and understanding of your pond manager he/she may be just giving you very generalized winter, aeration, vendor directions rather than the specific winter aeration / oxygenation needs of your pond.

Thanks for the reply, Bill. The pond is 1 acre in size, 14ft deep consistently. It was an old quarry that filled up naturally with water. There is a lot of built up muck and leaves on the bottom of the pond. There are a few trees around the edges that drop leaves, but not so many. Water clarity is around 6-8ft visability with this being close to the clearest time of year. Visibility drops a lot in the summer. No dye has been used for 2 or three years, but we did do two treatments of Nature's Pond Condition as recommended by our pond manager. I will link the product here. https://www.naturespondcare.com/products/pond-conditioner.html We have two surface aerators and the one bubbler which is the only one running since November.

Pond is stocked with 80 brown trout last fall (2020, 8-10" fish) as well as around 50 8-10" rainbows spring of 2021. There are some older browns from 4 years ago that are still around. Fish are pellet fed but have not really been eating near the aerator since it's gotten colder.

Please let me know if you need any more info. Thanks again.

Last edited by Fyfer123; 01/08/22 12:41 PM.

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Fyfer - My pond is making more ice today because the ice is expanding upward and cracking. Ice yesterday was 3" thick as I walked on it.

Okay your pond has and maintains trout. That makes water quality and dissolved oxygen more important during ice cover. Trout as cold blooded critters do not require quite as much DO when water is 39F as they do when water is 60F-65F (5ppm) because their body metabolism is measurably less in 39F water compared to 65F water. The body metabolism is what consumes and requires the DO. Faster is more; less is less.

Measureable amounts of muck and leaves on the bottom speeds the loss of dissolved oxygen (DO) from water when 2" or more of snow covers the ice. Snow on ice significantly inhibits light penetration. Deeper snow eliminates light penetration. Light penetration stimulates phytoplankton to make DO under the ice IF and IF the phytoplankton receives sunlight through the ice.

If you want ice for skating, this is what I would do and still have a 95% chance of overwintering trout in the features of your specific pond.

Move the aerator into 3 to 5 ft of water for emergency aeration. Or leave it where it is. There should be a slow slope to sit the aerator or just let it hang along an almost vertical wall in 3-4ft of water.

Turn off the aerator.

Let the water freeze and when ice is safe to walk on 4"+ shovel or 6"+ snow blow off snow whenever it gets deeper than 3"(7cm). Remove enough snow for some ice skating area and this should be enough surface area to get enough light through the ice and into the water to allow phytoplankton to make DO to maintain the trout. The more snow that you can remove the better especially if the ice is cloudy on top. Usually cloudy top ice has glass clear ice below it. Water with 6-8ft of visibility still has lots of microscopic phytoplankton (tens of thousands per ounce of water) for winter DO production. Water with this amount of phytoplankton in 6ft+ clarity does not have significantly high plankton densities to cause rapid DO loss under snow covered ice. DO loss in dark does occur but not faster than several weeks. Your 14ft ave depth extends this time.

If the wind can blow snow off large areas of the pond then snow removal is not necessary. This is why frozen SHALLOW ponds exposed to strong winds and snow is regularly blown off rarely have winter fish kills. In my area we regularly have January or a February thaw and a noticalbe snow melt. This gets light back into the pond so the phytoplankton can again make and restore the DO.

Normally I like to get a pond surface area of 10% snow removed and for your 1 ac this is an area of around 65x65ft - around 4300 sqft. In small lakes snow is removed in alternating strips so sunlight penetrates the length of the lake or large pond.

Wood our Canada PB member in Manitoba or Saskatchewan had trout in his smaller, shallower pond than yours. Deep water holds more volume of DO compared to shallower 6-10ft of water. We educated him and he consistently and regularly shoveled snow off the ice that was a whopping 3 ft thick. This snow removal allowed light to penetrate through the 3 ft of ice for the phytoplankton to make DO to keep the trout alive. Wood sold the property so he regretfully is no longer is a PB member. Maybe I can find a link to his PB threads about his pond and snow removal success story.

In a pond such as yours with ave depth of 14ft containing trout and clear water, snow does not need to be removed until snow of 3"+ lies on the ice for longer than 4 weeks. Now at this point DO starts to be slowly or gradually lost from the bottom towards the top. Length of time until the DO is lost at just under the ice through 14 ft can take a few more weeks. However since you have trout be concerned when a snow blanket lays on your pond longer than 4 weeks.



Then at 4 weeks or more conservatively 3 weeks, ,,, START your aerator that has the diffuser in 3ft of water and let it run until it opens a hole 6ft-10ft dia or more in the ice. Turn off the aerator. Thereafter then run the aerator each day just long enough to reopen the 6-10ft dia hole.

Last edited by Bill Cody; 01/09/22 05:10 PM.

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Fyfer,

You have already gotten advice from experts far more knowledgeable than I, but no one has talked about the strength and direction of your prevailing winds.

Is your aerator location "upwind" from the bulk of your pond? Water ice can sometimes have strange crystallization manifestations. Is there a chance that you are making a little bit of slush with entrained air bubbles at the aerator and the wind is pushing it around the rest of the pond? That could be preventing the formation of your solid "skating" ice.

You might be able to change the location of your aerator, with the result being DO for your trout AND solid ice for human recreation.

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Originally Posted by Bill Cody
Fyfer - My pond is making more ice today because the ice is expanding upward and cracking. Ice yesterday was 3" thick as I walked on it.

Okay your pond has and maintains trout. That makes water quality and dissolved oxygen more important during ice cover. Trout as cold blooded critters do not require quite as much DO when water is 39F as they do when water is 60F-65F (5ppm) because their body metabolism is measurably less in 39F water compared to 65F water. The body metabolism is what consumes and requires the DO. Faster is more; less is less.

Measureable amounts of muck and leaves on the bottom speeds the loss of dissolved oxygen (DO) from water when 2" or more of snow covers the ice. Snow on ice significantly inhibits light penetration. Deeper snow eliminates light penetration. Light penetration stimulates phytoplankton to make DO under the ice IF and IF the phytoplankton receives sunlight through the ice.

If you want ice for skating, this is what I would do and still have a 95% chance of overwintering trout in the features of your specific pond.

Move the aerator into 3 to 5 ft of water for emergency aeration. Or leave it where it is. There should be a slow slope to sit the aerator or just let it hang along an almost vertical wall in 3-4ft of water.

Turn off the aerator.

Let the water freeze and when ice is safe to walk on 4"+ shovel or 6"+ snow blow off snow whenever it gets deeper than 3"(7cm). Remove enough snow for some ice skating area and this should be enough surface area to get enough light through the ice and into the water to allow phytoplankton to make DO to maintain the trout. The more snow that you can remove the better especially if the ice is cloudy on top. Usually cloudy top ice has glass clear ice below it. Water with 6-8ft of visibility still has lots of microscopic phytoplankton (tens of thousands per ounce of water) for winter DO production. Water with this amount of phytoplankton in 6ft+ clarity does not have significantly high plankton densities to cause rapid DO loss under snow covered ice. DO loss in dark does occur but not faster than several weeks. Your 14ft ave depth extends this time.

If the wind can blow snow off large areas of the pond then snow removal is not necessary. This is why frozen SHALLOW ponds exposed to strong winds and snow is regularly blown off rarely have winter fish kills. In my area we regularly have January or a February thaw and a noticalbe snow melt. This gets light back into the pond so the phytoplankton can again make and restore the DO.

Normally I like to get a pond surface area of 10% snow removed and for your 1 ac this is an area of around 65x65ft - around 4300 sqft. In small lakes snow is removed in alternating strips so sunlight penetrates the length of the lake or large pond.

Wood our Canada PB member in Manitoba or Saskatchewan had trout in his smaller, shallower pond than yours. Deep water holds more volume of DO compared to shallower 6-10ft of water. We educated him and he consistently and regularly shoveled snow off the ice that was a whopping 3 ft thick. This snow removal allowed light to penetrate through the 3 ft of ice for the phytoplankton to make DO to keep the trout alive. Wood sold the property so he regretfully is no longer is a PB member. Maybe I can find a link to his PB threads about his pond and snow removal success story.

In a pond such as yours with ave depth of 14ft containing trout and clear water, snow does not need to be removed until snow of 3"+ lies on the ice for longer than 4 weeks. Now at this point DO starts to be slowly or gradually lost from the bottom towards the top. Length of time until the DO is lost at just under the ice through 14 ft can take a few more weeks. However since you have trout be concerned when a snow blanket lays on your pond longer than 4 weeks.



Then at 4 weeks or more conservatively 3 weeks, ,,, START your aerator that has the diffuser in 3ft of water and let it run until it opens a hole 6ft-10ft dia or more in the ice. Turn off the aerator. Thereafter then run the aerator each day just long enough to reopen the 6-10ft dia hole.

Thank you for the very detailed reply. We do get a lot of snow and very cloudy ice due to the fact that cold temperatures here almost always result in lake effect snow from Georgian Bay (Lake Huron). However, we always keep a shoveled area about as large as you mentioned for skating. I also keep some other areas shoveled so I can walk and fish. We have had one small fish kill after ice out a couple of winters ago but the pond generally seems to support trout all year round. Some trout have been there almost 5 years.

In regards to the aerator, is there is problem turning it on now or in a few days? I have not had a chance to check, but I'm almost sure that the area that it kept open is frozen over and safe to walk on now. Additionally, it is currently at the bottom in 14ft of water because we have no shallow areas of the pond. The walls are straight drop offs. What is the benefit of making it hand midway down the water column?

Thanks again.


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Originally Posted by FishinRod
Fyfer,

You have already gotten advice from experts far more knowledgeable than I, but no one has talked about the strength and direction of your prevailing winds.

Is your aerator location "upwind" from the bulk of your pond? Water ice can sometimes have strange crystallization manifestations. Is there a chance that you are making a little bit of slush with entrained air bubbles at the aerator and the wind is pushing it around the rest of the pond? That could be preventing the formation of your solid "skating" ice.

You might be able to change the location of your aerator, with the result being DO for your trout AND solid ice for human recreation.

Thanks for the reply. Our winds do change a lot but I would say the prevailing winds would push any slush produced in part by the aerator towards the shore, so I assume that is not bad for ice formation. However, our ice would usually be solid by now and thus if the aerator was turned off briefly I assume that it wouldn't matter where new slush was pushed? Thanks again.


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Fyfer - As long as you can keep similar amounts of snow removed from the ice you should not need to run the aerator during ice cover. Those fish that died during winter might have been real old fish that died from high body stress during long cold winters. Winters are very hard on the oldest fish or those near the end of their life that tend to get weak during hard winters.
Moving the diffuser head close to the surface and hang along the vertical wall during winter mixes less of the deepest bottom water. Mixing mostly the upper layer in winter still provides open surface water for light penetration, DO production and for less benefit of decomposition gas to escape. Mostly the surface water in winter provides or maintains the warm 39-40F (4C) water in the deep water. The shallower you can place the diffuser the more unmixed bottom water remains as a warm zone. Diffuser on the bottom tends to mix the entire water column producing super cool water to temps below 4C. Fish will have less cold stress if 39F water is available.

Last edited by Bill Cody; 01/11/22 08:01 PM.

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Originally Posted by Bill Cody
Fyfer - As long as you can keep similar amounts of snow removed from the ice you should not need to run the aerator during ice cover. Those fish that died during winter might have been real old fish that died from high body stress during long cold winters. Winters are very hard on the oldest fish or those near the end of their life that tend to get weak during hard winters.
Moving the diffuser head close to the surface and hang along the vertical wall during winter mixes less of the deepest bottom water. Mixing mostly the upper layer in winter still provides open surface water for light penetration, DO production and for less benefit of decomposition gas to escape. Mostly the surface water in winter provides or maintains the warm 39-40F (4C) water in the deep water. The shallower you can place the diffuser the more unmixed bottom water remains as a warm zone. Diffuser on the bottom tends to mix the entire water column producing super cool water to temps below 4C. Fish will have less cold stress if 39F water is available.

That makes sense regarding mixing the water temperatures. We did however install the aerator as recommended by a pond manager not for the fish but to prevent spring weed growth by allowing gasses to escape. Do you have any comments on how effective the aerator will be at preventing spring weed growth, which is a major problem in our pond. We have curly leaf pondweed which we have discussed before. You had recommended various herbicides such as diquat but they are simply impossible to acquire or apply here, so this was our only choice. Thanks again.


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how effective the aerator will be at preventing spring weed growth,

I have never seen nor read any scientific based information or peer reviewed research about how bottom aeration will prevent spring submerged weed growth that would include curly leaf pond weed. I will assume the person who told you this,,,,, wants or plans for you to run the aerator 24/7. IMO 24/7 bottom aeration is often not necessary - depending on pond conditions, pond goals, and pond location.

Based on my extensive aquatic biology education(MS) with an emphasis in algae, I do not understand the rationale for how the bottom aeration will slow or prevent submerged weed growth. Aeration is "said" or promoted to inhibit phytoplankton growth especially harmful planktonic algae such as some of the Cyanobacteria species. This could be possible by tending to keep the floating nuisance types of tiny algae more in suspension. which it does not prefer. NOTE there are some Cyanobacteria problem types that will do well in mixing water. Be aware of sales 'Generalizations'. Mixing water could somewhat inhibit vulnerable types of algae providing the mixing currents are strong enough in the entire pond/reservoir. IMO in most all cases there would still be areas of most all ponds where slack / calm water exists. Thus the current mixing influence would be minimal in these areas. Is your pond adviser calling phytoplankton "submerged weed growth"?. I hope not.

There has been IMO a common misconception or limited research that aeration will reduce phosphorus (P) in ponds. This P reduction in the water column might occur but IMO it is to a small degree. If aeration could significantly reduce P there would be not a need for P reducing chemical products! Palm to forehead. If aeration really worked well, ponds with aeration would not develop algae problems. I have seen way too many ponds with aeration and them that are extensively covered with or containing nuisance algae problems. A good example is the FA alga Cladophora that is considered a P "hog". Cladophora as a warm water, long day length alga can grow really, really well diring summer / fall in ponds with good aeration. It can even overwinter in ponds for a resurge in warmer water. IMO Cladophora likely removes a LOT more P from the water than the aerator.

The other factor of aeration reducing weed growth to occur is this. Bottom aeration is designed to prevent stratification. Preventing stratification minimizes the production and release of P from the anoxic / anaerobic sediments. Destratification via aeration is said to reduce the amount of P(phosphorus) in the water column which would in theory tend to "starve" phytoplankton. This influence can be attributed to why some ponds clear up after aeration is installed. Maybe, maybe not. I question the degree or amount of P inhibition by aeration of the water column. Dissolved or reactive P from the sediments has a + charge and the ion is looking for - charged particles / ions which it often soon locates and then P becomes chemically bound, often to silt or carbonates, and it is then unavailable to plants. Plants require dissolved P (ortho P) for absorption and growth. Submerged plants obtain a lot of their P from the sediments with also a portion dissolved in the water column (aka a form of foliar feeding via their leaf epidermis and stoma) depending on the type of plant. So IMO curly leaf pond weed likely gets most of its N+P from the sediments because it is a rooted plant and that is what rooted plants do. So then,,,, knowing all this,,,, what is the justification for bottom aeration suppressing submerged weed growth? Specifically I would like to know just how does this happen????

Based on what you now know, I would definitely contact your pond advisor / manager and ask for an explanation of how the aerator actually slows, or prevents weed growth. I would definitely like to hear that information. How sound and accurate is that advice?? If that advice is not accurate how much of the manager's advice can you trust? What is the basis of his knowledge?? I have seen many weed choked and green water ponds with active bottom aeration. How are your pond weeds doing now after installing the aerator???? Curly leaf pond weed has a natural growth cycle. Rapid growth in spring until it flowers and produces seeds and turions. Thereafter a death collapse phase in mid late summer. Sprouting germination phase in fall. Dormancy in winter. Rapid growth in spring when water gets above 50-60F(10C+).

Last edited by Bill Cody; 01/12/22 03:29 PM.

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Originally Posted by Bill Cody
Quote
how effective the aerator will be at preventing spring weed growth,

I have never seen nor read any scientific based information or peer reviewed research about how bottom aeration will prevent spring submerged weed growth that would include curly leaf pond weed. I will assume the person who told you this,,,,, wants or plans for you to run the aerator 24/7. IMO 24/7 bottom aeration is often not necessary - depending on pond conditions, pond goals, and pond location.

Based on my extensive aquatic biology education(MS) with an emphasis in algae, I do not understand the rationale for how the bottom aeration will slow or prevent submerged weed growth. Aeration is "said" or promoted to inhibit phytoplankton growth especially harmful planktonic algae such as some of the Cyanobacteria species. This could be possible by tending to keep the floating nuisance types of tiny algae more in suspension. which it does not prefer. NOTE there are some Cyanobacteria problem types that will do well in mixing water. Be aware of sales 'Generalizations'. Mixing water could somewhat inhibit vulnerable types of algae providing the mixing currents are strong enough in the entire pond/reservoir. IMO in most all cases there would still be areas of most all ponds where slack / calm water exists. Thus the current mixing influence would be minimal in these areas. Is your pond adviser calling phytoplankton "submerged weed growth"?. I hope not.

There has been IMO a common misconception or limited research that aeration will reduce phosphorus (P) in ponds. This P reduction in the water column might occur but IMO it is to a small degree. If aeration could significantly reduce P there would be not a need for P reducing chemical products! Palm to forehead. If aeration really worked well, ponds with aeration would not develop algae problems. I have seen way too many ponds with aeration and them that are extensively covered with or containing nuisance algae problems. A good example is the FA alga Cladophora that is considered a P "hog". Cladophora as a warm water, long day length alga can grow really, really well diring summer / fall in ponds with good aeration. It can even overwinter in ponds for a resurge in warmer water. IMO Cladophora likely removes a LOT more P from the water than the aerator.

The other factor of aeration reducing weed growth to occur is this. Bottom aeration is designed to prevent stratification. Preventing stratification minimizes the production and release of P from the anoxic / anaerobic sediments. Destratification via aeration is said to reduce the amount of P(phosphorus) in the water column which would in theory tend to "starve" phytoplankton. This influence can be attributed to why some ponds clear up after aeration is installed. Maybe, maybe not. I question the degree or amount of P inhibition by aeration of the water column. Dissolved or reactive P from the sediments has a + charge and the ion is looking for - charged particles / ions which it often soon locates and then P becomes chemically bound, often to silt or carbonates, and it is then unavailable to plants. Plants require dissolved P (ortho P) for absorption and growth. Submerged plants obtain a lot of their P from the sediments with also a portion dissolved in the water column (aka a form of foliar feeding via their leaf epidermis and stoma) depending on the type of plant. So IMO curly leaf pond weed likely gets most of its N+P from the sediments because it is a rooted plant and that is what rooted plants do. So then,,,, knowing all this,,,, what is the justification for bottom aeration suppressing submerged weed growth? Specifically I would like to know just how does this happen????

Based on what you now know, I would definitely contact your pond advisor / manager and ask for an explanation of how the aerator actually slows, or prevents weed growth. I would definitely like to hear that information. How sound and accurate is that advice?? If that advice is not accurate how much of the manager's advice can you trust? What is the basis of his knowledge?? I have seen many weed choked and green water ponds with active bottom aeration. How are your pond weeds doing now after installing the aerator???? Curly leaf pond weed has a natural growth cycle. Rapid growth in spring until it flowers and produces seeds and turions. Thereafter a death collapse phase in mid late summer. Sprouting germination phase in fall. Dormancy in winter. Rapid growth in spring when water gets above 50-60F(10C+).

Thanks for the detailed reply, Bill. I appreciate all of the information. The pond manager indicated that we should only run the aerator during ice cover or around times when ice cover is possible. Because we do not want to destratify the water during the summer when the trout need cold water at the bottom, we do not plan on running it after ice out. The logic of the aerator, as far as I understand, was just to keep some area of the pond open during the winter to reduce spring weed growth. I am not sure as to why that is supposed to work. Is keeping some water open on ponds that are frozen for a fairly long time a way of reducing weed growth. The whole management strategy for pond weed from this manager revolves around reducing excess nutrients in the pond that cause weeds to grow. As I said, a approved product is being used to reduce nutrients called Nature's Pond Conditioner (see link in previous post on this thread). Again, any input is really appreciate. Thanks again.


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Bill:

Let me get with you on some information regarding O2 to reduce the amount of P in the water. I have some data to run past you.


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Fyfer says:
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The logic of the aerator, as far as I understand, was just to keep some area of the pond open during the winter to reduce spring weed growth. I am not sure as to why that is supposed to work. Is keeping some water open on ponds that are frozen for a fairly long time a way of reducing weed growth.

I think keeping ice and snow cover less in a pond with curly leaf pondweed will enhance not hinder the growth of curly leaf. Curlyleaf is considered a cool water plant. Plants need sunlight for good health. So my thinking is more light to them due to more open water in winter helps them survive not hinder them.

Your manager suggested product of Nature's Pond Conditioner is very likely an enzyme + microbial bacterial product. According to Dr. Claude Boyd, as a distinguished and well known, extensively published professor emertius in School of Fisheries, Aquaculture & Aquatic Sciences, Auburn University in Alabama, USA, Bacterial Amendments do not enhance water quality in ponds. Dr. Boyd regularly writes a water quality article in every PBoss Magazine.

In his Nov-Dec 2017 Pond Boss magazine article - "Do Microbial Amendments Improve Water Quality in Ponds?", he says he tested microbial amendments in several studies in aquaculture and sportfish ponds. Tests showed very few instances where the concentration of one or more water quality variables improved following additions of bacterial based products in lab and pond studies. In addition bacterial ABUNDANCE was similar in treatment and non-treatment ponds. He concluded scientific evidence and logic also do not support use of bacterial amendments as a means of improving water quality in ponds. My studies and experience tend to agree with Dr.Boyd's conclusions. The main exception I have found is bacterial amendments are useful in ponds that have been routinely treated with algaecides and herbicides that damage and degrade the bacteria community. Amendments could help reestablish and 'kick start' normal healthy bacterial communities in compromised waters.

My "take" on these amendments is none of these products will state what is in the product. IMO this is primarily because almost all or all of them are just using natural bacteria cultures that are known natural decomposers that naturally occur in uncompromised habitats / ponds /lakes where the bacteria species originated to create the cultured products. Thus in natural healthy environments nature has all the necessary bacterial species present to keep it healthy and functioning as it has for eons prior. Human activities can damage these natural bacterial communities and sometimes seeding or recolonization may be necessary or beneficial.

Dr. Boyd has an excellent water quality book recently published and all serious pond managers should have and thoroughly understand this easy to read book. Ignoring it is negligent. Ask your pond manager if he has Dr. Boyd's book: Handbook for Aquaculture Water Quality. His answer may provide some insight into the background and water quality knowledge about his advice. I also have one of DrBoyd's earlier more technical books titled Water Quality in Ponds for Aquaculture (1990).

Technically running the aerator placed on the bottom in winter also destratifies the pond, but instead of making the pond warmer on the bottom it makes the bottom colder by mixing coldest surface atmosphere exposed cooled water toward the bottom that normally remains 4C during winter. I have measured winter bottom aerated water temps down to 33F, 6 degrees colder than 39F. This colder temp than 39F(4C) toward 32F(0C) does little harm to the trout as it would to other warm water fish such as bass and catfish. You could experiment with moving the diffuser closer to the surface to test which depth produces the quickest and largest open water area if you decide to run the compressor fewer hours per day to just daily create a zone of ice free water and allow light penetration. As long as the ice free area freezes with clear snow free ice,,,, light will readily penetrate the water in this clear ice area and open water is not really needed until the area again becomes snow covered.

Last edited by Bill Cody; 01/12/22 08:51 PM.

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Regarding dissolved oxygen, at what ppm do I need to be concerned, start aerator or engage in other emergency measures. Pond has trout, bluegill and yellow perch. I lost most of my trout and a few larger bluegill last winter, so I am monitoring DO. I have a small aerator, battery operated, and I can add water to the pond from irrigation piping, but that is risky in extreme cold. Things tend to freeze and break.


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Trout aren't happy with less than 7 mg/l DO. 5mg/l is pushing their limit.


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Thank you! I’m on the cusp right now, so emergency measures have started.


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esshup says "Trout aren't happy with less than 7 mg/l DO. 5mg/l is pushing their limit."

This information is true for normal water temperatures of 50-65F that are preferred by trout. However I am not sure that 5ppm is the lower DO limit for trout when water temperature is 39F or lower. My EPA water quality criteria book says for DO: 1. "fish vary in their oxygen requirements according to species, age, activity, temperature, and nutritional state. 2. fish are found from time to time and can survive for awhile at oxygen concentrations considerably below that considered suitable for a thriving population;" They (EPA manual) goes on to say that "few investigators have employed methods or sought endpoints that can be related with confidence to maintaining a good fish population."

Trout are not perch or other similar type of fish species but my DO testing shows that YP and some other fish species at 35F-39F will tolerate dissolved oxygen down to 1ppm and even less when normally 3ppm is said to be their lower limit for DO. I think a similar fish physiology response would apply to trout. As their body temperature decreases below their preferred temperature,,, their body physiology also decreases, and their cellular demand for oxygen also decreases. Although the lower DO limit for trout in 39F water would MAYBE be closer to 3 or 4ppm rather than 5ppm. We might be surprised that rainbow trout can even tolerate 2 - 2.5 ppm DO in water 37-39F (3-4C).

I would very much like to find research or any private testing that shows the lower DO limit for trout in water temps less than 39F (4C). I have worked very little with trout in ice covered ponds thus my testing of this feature is very limited. We have to remember that under ice cover when the pond is in the later stages of DO consumption the DO is continually decreasing and DO usually does not stabilize at 3, 2, or 1ppm. Thus the time frame is usually relatively short for low DO that would sustain trout or any fish.

Last edited by Bill Cody; 01/14/22 12:02 PM.

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Bill:

I'm not saying that I am disagreeing with you. If you had to put a time limit on those DO numbers where the trout would survive, how long (days) do you think they could survive in those DO levels? (at the 35°F-42°F water temp range)


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Once again, I really appreciate the reply, Bill. You have definitely given me a lot to think about. I will have to discuss this with the pond manager. We were hoping that these changes (aerator and pond bacteria product) would help our weed problem. As of now, our aerator is off and I am testing the ice tomorrow to see how it formed. It's currently -19C (-2.2F), so I think the ice should be good for fishing and skating. All lakes around me are frozen with 8+" of ice at least. Thanks again for the help and I will update as new information comes.


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Fyfer - When I get air temps at -12C (10F) my pond creates 1" ice per night.

esshup says
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If you had to put a time limit on those DO numbers where the trout would survive, how long (days) do you think they could survive in those DO levels? (at the 35°F-42°F water temp range)

So based on what I found on the web (see below), at 35F-39F and DO stays at a steady 2.5 to 3ppm (mg/L), I think the trout would survive for at least 3 to 4 weeks. The main problem is when ponds are ice covered and losing DO due to extended snow cover the dissolved oxygen is in a continual steady decline or decrease due to the lack of sunlight stimulating DO production by plant photosynthesis. Also remember usually the DO loss begins at the bottom sediments and DO loss moves upward toward the ice layer. The fish are forced into shallower and shallower water as the DO is extinguished until the entire pond DO decreases to lethal concentrations depending on species tolerance to low DO. Trout will normally be first fish to die because they can not locate survivable DO concentrations.

DO loss and production under ice-snow cover is highly variable from gradual to sudden dependent on the pond eutrophy and conditions; IMO- biochemical oxygen demand. In Pasinski's pond on Feb 12 DO under the ice fell from 12.3 to 2.ppm on Feb 14; a 5ppm loss per day. whereas on Green Lake under ice on Feb 5 DO increased from 1.8ppm to 8.0ppm on Feb 8 in 3 days a rate of 2.7ppm per day due to photosynthesis when snow was removed from the ice.

A little web searching I found:
The 1985 EPA Water Quality book says " Although the acute lethal limit for salmonids is at or below 3 mg/L, the coldwater minimum has been established at 4 mg/L because a significant proportion of the insect species common to salmonid habitats are less tolerant of acute exposures to low dissolved oxygen than are salmonids.
And I found this - Although O.mykiss (rainbow) have been recorded in a range of dissolved oxygen levels of 2.6 - 8.6 mg/L (Thurston et al. 1981),

A summary of various field study results by WDOE (2002) for trout reports that significant mortality occurs in natural waters when dissolved oxygen concentrations fluctuate the range of 2.5 - 3 mg/L. Long-term (20 - 30 days) constant exposure to mean dissolved oxygen concentrations below 3 - 3.3 mg/L is likely to result in 50% mortality of juvenile salmonids (WDOE 2002). North Coast Regional Water Quality Control Board.. IMO longer survival times will occur at DO of 2.5 to 3mg/L when water temperature is close the the 39F-40F.

Lower temperature limits.
Highest mean temp maximum and lowest mean temp minimum measured over these acclimation temperatures were 40.3 and 2.7 °C (catfish), 38.5 and 3.2 °C (bass) and 29.8 and ∼ 0.0 °C (trout). . I did not have the entire article so I do not know if 0C was the lowest temperature used for trout. Water moving will not freeze at 32F (C).

Currie, R.J., W.A. Bennett, T.L. Beitinger. 1998. Critical thermal minima and maxima of three freshwater game-fish species acclimated to constant temperatures. Env. Bio. of Fishes 51:187-200.

Last edited by Bill Cody; 01/14/22 09:45 PM.

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At those temps you should get thick ice pretty quickly.

How about using your chainsaw to cut out a 4' x 4' square of ice above the aerator after you get good ice across the pond?

Then you might have happy trout and happy kids!

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