Pond Boss Forums AERATION Systems questions Is aeration always necessary?

Thank you everyone for sharing your expertise/successes (or "learnings"!) on this forum. My neighbors and I live on a 15 acre pond in northwestern WI. We have LMB, P, BG. The deepest part of the pond is 13' deep and the average depth seems to be 6-7'. This is a new development (around an existing pond) and we want to do the right things from the start. From reading other threads on this forum, I know we need to test our pH and O2 levels. We're starting that investigation now.

What do fellow northern pond owners say about aeration? I know most of you have private, smaller ponds. I really like your ideas for your ponds. If we're worried about fish kill, does it even make sense to try to put in an aeration system? I've read in some of your posts about the Vertex system. That seems to be top of the line and it works for you. If we run electricity down to the pond, would it be worth the investment for a four of five diffuser system? On the Vertex website, it says it's best for 2-3 acre ponds.

So what do you think? Aeration - necessary or not for a 15 acre pond? Thanks everyone.

I give you a definitive yes. What I don't know is how much you should worry about a fish kill in a 15 acre pond in North Cheeseland. But you'll hear about that from more knowledgeable pondmeisters. Dr. Mark Cornwell's articles ("On Northern Pond") in (back issues of) PBMag will likely have some valuable info along those lines, too.

Remember you could place the compressor where you already have electric, and run air to the pond, for less moolah.

WiPondGuy – 15 acres of water is a lot of water and very expensive to try and aerate and create turnovers.

IMO before you spend money on aerating a 15 ac pond/lake, here is what I think you should do before Sept 15 and IT is BEST done in August. You want to do this before the cool weather changes the 'Normal" mid-summer temperature - oxygen features of your 15 ac pond. If you don't get it done this year then schedule it for next year July-August before you decide to aerate this 15 ac of water.
Do or have it done as a temperature - dissolved oxygen profile survey in various parts of the pond. Also Create a depth contour map of the pond with the temperature and DO measurements every 1-2 ft deep. These data will tell you where the thermocline is (depth) and what areas in the pond usually in mid-summer have the least amount of dissolved oxygen (DO) and MAY need to be aerated.

AS the pond and all ponds age and weather conditions change these data will change sometimes dramatically, usually toward poorer conditions in a more eutrophic older pond during mid- summer is when summer fish kills are more frequent. Extended snow cover in longer WI winters also makes winter kills more likely.

You say - "The deepest part of the pond is 13' deep and the average depth seems to be 6’-7'." For a large pond, One really needs to know what percentage of the pond is not being naturally circulated by wind action and where those areas or sections are located for an educated decision to aerate or not aerate. This is especially true for large ponds 10+acres and relatively shallow as 10ft to 15+ft deep.

If I don't miss my guess from your brief pond description, and IF the pond gets periodic good wind action across 15 acres and there are occasional 6" high waves or almost white caps then all areas of the pond that are 6ft to maybe 12 ft deep should have decent natural water mixing. DO testing will tell you this natural mixing depth. However a pond in a wooded area with little or no direct wind action then likely poor natural vertical water circulation occurs. Wind action on the pond determines the depth that wind is able to mix the warm surface layer into the cooler deeper depths. Water temperatures also affect this mixing depth. Water clarity affects natural depth of DO production.

The volume of pond water or percentage of total pond water with DO near 0 will determine the chance of fish kill. The more deep anaerobic water in July-August that is present that could get mixed into the good DO water above will really determine if bottom aeration is needed in this pond. It is this anaerobic water that causes fish kills. IMO if the pond has less than 10% to maybe 20% of the water as anaerobic conditions then IMO I would not aerate this pond. Or as an alternative I would just mix only the deepest zone depth/s to keep that anaerobic water pushed to the surface where it gets degassed and oxygenated in the epilimnion layer.

Bill (and all others),

How effective are large freshwater fish at detecting oxygenated water at a distance?

For example, if you can only aerate 20% of a pond, will the fish tend to migrate from their favorite spots to the oxygenated water during a crash event? Or is the diffusion of oxygen into the depleted oxygen waters so miniscule that the fish may die while 100' away from good water?

I wonder if there could be pond design implications with a partial aeration system. Say you had a deep water refuge that was subject to thermoclines which basically becomes unusable in the summer months. If you were able to mix from the deep area what would happen to usable area and water temps as a result. Just me thinking out loud. I don't have an answer to the question.

Question from FishinRod "..... if you can only aerate 20% of a pond, will the fish tend to migrate from their favorite spots to the oxygenated water during a crash event? Or is the diffusion of oxygen into the depleted oxygen waters so miniscule that the fish may die while 100' away from good water?"
IMO no - the fish will not migrate with the intention to get more DO water. 1. HOw will they remember where the higher DO is? 2. I am pretty sure they cannot detect higher DO 20 ft away. I've watched fish dying and not getting enough oxygen. IMO they aimlessly swim about 'gasping' for more oxygen. 3. They might find the higher DO water but only by accident. 4. It might be possible that the water in a certain spot always has higher, thus the fish frequently visit the area with higher DO. Possible but very doubtful in my mind. 5. Oxygen diffuses very, very, very slowly in water. Currents are mainly responsible for spreading and moving the DO in water.

Question from Boondoggle - " a deep water refuge that was subject to thermoclines which basically becomes unusable in the summer months. If you were able to mix from the deep area what would happen to usable area and water temps as a result."

Let's see IF I understand the question correctly. " what happens to the surface usable zone and the water temps when you mix colder anaerobic no DO water up into the surface zone?"

For a normal bottom diffuser aeration system that rising currents of bubbles mix bottom to top, Some of this depends on how much volume of anaerobic water is mixed upward into the top layer. The anaerobic cooler water dilutes the surface water and lowers its temperature; depends on flow volume. This degrades the quality of surface water with no DO in the water and the hydrogen sulfide gas is very toxic to fish. Each factor separately can kill fish. A double wammy for fish happens who now cannot get enough oxygen and also the H2S poisons them. The cannot 'breathe' and have to deal with a poison. If the surface water is degraded enough lowering or diluting the DO and the H2S is concentration is high enough fish die.

However there are aerators called hypolimnetic aerators that mix only the deep cooler water. I wrote a term paper (grade A+) about this for graduate school limnology class. I am currently testing a new design for a guy in PA for this type of aerator to oxygenate only the cool deep zone. Also Pond boss magazine has had a couple recent articles about new versions of hypolimnetic aerators. IF you don't subscribe to PBoss magazine you should and your pond will be better for it. Editor Bob Lusk and I together have an article about stocking a new pond for the Sept-Oct PBoss mag issue.

Thanks for all of that great info.

I didn't think the fish could sense higher DO water. I also didn't think they randomly circled over a lot of territory once they started piping such that they might luck into oxygenated waters that would save their life.

My interpretation of Bill Cody: If you are going to aerate a small pond to avoid fish kills, then you need to aerate the WHOLE pond.

Of course, the original post was contemplating aeration for 15 acres, which to me qualifies as a large pond. The wind-driven surface wave aeration on a 15-acre pond might be a whole order of magnitude greater than the mixing on a 3/4 acre pond. When the wind is blowing!

WiPondGuy, do you ever have a pond management person visit your pond or have an expert deliver your fish when you do a new stocking? If so, you might ask them to bring a good DO meter and test your pond in a few spots and depths and start collecting some data. More data always helps make a better decision.

Years ago I was contacted by a HOA that had an 18 ac lake that experienced summer and winter kills. The first year all they could afford was a Vertex system that would aerate 9 acres. The 2nd year they had a summer kill in the un-aerated half. So that proves to me that the fish won't move to higher levels of O2 in a pond.

WiPondGuy, how old is the pond? How much muck has accumulated on the bottom? What is the water clarity like during different times of the year?

Great info on several questions, esshup!

Thanks again for your in-depth answers to my questions on our 15 acre pond/lake. You had a couple follow-up questions for me.

1) Have we talked to a pond management person? We have, but he wants to charge $1,750 for a general walk-around assessment. We didn't think we would get a ton of benefit from that but I'm willing to hear your thoughts on a review like that. He also gave us a sample report from another unnamed lake that went into great detail, but the cost was $13,500 and that seemed a bit steep. It would provide all of the data that you guys have been talking about, however. We didn't use an expert when our bass and bluegills were delivered. That was more of a "grassroots" endeavor!

2) How old is the pond? The pond has been here for decades. It's a seepage pond that seems to vary from 8 to 17 acres according to old Google Map photos. One person who lives a couple miles away told me that 20 years ago, it was dry. Our Google Map research didn't go back that far to see if that was accurate. The six new houses on the lake are 1-3 years old. When all the lots are sold, there will be 12 houses around the lake

3) How deep is the muck? I'd say pretty deep. When I put in the dock, I'd say it was calf deep in a lot of spots. The lake still has a lot of vegetation around the lake

4) Water clarity at different times? I think the clarity is pretty good. Most of the time when I kayak, I can see the bottom at 6'. The water is still pretty clear now, but the weeds have really grown in this year.

Here is what I've taken away from all of your responses: 1) I need to subscribe to Pond Boss magazine (done, for two years!). Like Theo mentioned above, there are past articles that will help me that I need to order 2) We need to test the pH levels. We've ordered some pH testing kits. 3) Test our DO levels ASAP before the lake turns over. Are there simple ways to do that? Do you guys use at homes DO testing kits? If so, which ones?

Thanks again to everyone

IMO you will not get $1700 worth of information for a walk around.
If the pond continually has water clarity of 6ft then enough sunlight will reach the bottom for phytoplankton and plants to make dissolved oxygen on the bottom in 13ft of water. More turbid water will not allow DO to be produced on the bottom deep zone and a minor fish kill could result during summer periods of more turbid water. As I noted, the volume of anaerobic water in the deep zone will determine how much of a fish kill would occasionally happen and if an aeration system would be a good investment or even needed.

I think this old sediment nutrient laden shallow clear water pond will be a money pit because it will take lots of money each year to keep the weeds and algae controlled to make the pond useable and look ‘good’. Buying an aeration system for this pond would just be the start of lots and lots of annual management expenses for this relatively old aging pond.

IMO if I lived on a pond like you describe I would consider selling my property. This old shallow pond with lots of shallow water and thick organic nutrient laden sediments that water often has 6 ft of clarity is a continual weed factory that will always be causing more and more greenery problems that could be quite expensive to manage it to have only a few weeds – algae. Weeds and algae will want to grow more each year not less because of the nutrient enriched condition and accumulating more nutrients each year.. Weeds and algae can easily grow 12-13ft deep when water has clarity of 6ft. All ponds are nutrient collection basins that every year get more and more enriched to grow more and more plants. It no doubt harbors lots of geese and ducks. 10 geese make the manure of one cow. Plus during dry periods the 15 acres of water could be 8 acres or less. Ideally IMO this pond should be drained and rebuilt with steeper banks and get rid of all the years of accumulated deep, organic, nutrient, enriched, sediments out, and get more of an average depth of 10-12ft to reduce weed / algae problems. This pond is a money pit.

Home DO testing units will not measure accurately water collected from the depths unless you use special collection methods for the subsurface water. When you bring water from the subsurface and expose it to the air to test it ,,,,this adds DO to the water and gives an inaccurate false reading.

One option is to do the pond depth map yourself spend around $900 to buy a YSI Dissolved Oxygen - Temperature meter (DO200ACC-10) with a 12 ft long probe sensor from Zoro. Do the water DO temperature profile yourself. YSI are good reliable DO-Temp units that could be later resold for decent money. There are other cheap DO meters on the Web that reselling the unit might not get much money.
Or Amazon --- YSI 55 Handheld Dissolved Oxygen Meter with 50' Cable and Probe,$700.00

Bill - Thank you very much for the honest assessment. What I've gathered from the responses to my post and from conversations in other threads, you're absolutely correct that this pond/lake could very well be a money pit if we let it. We love the house, so selling won't be an option!

I went out and kayaked last night and paid attention to water clarity. I'd say I could only see the tip of the paddle at 2.5'. So visibility is 6' in spring/early summer and 2.5' now. From your response, maybe less visibility at this time of year is actually a good thing.

I think I'll check with the pond management guy to see if he has the equipment to do the pH & DO testing. We don't need the full blown lake assessment but maybe he could get us info on those two readings.

Thanks again everyone for taking such an interest in our little lake!

For what your assessment guy charges, you could buy a pretty nice DO meter for your self.

Once you get your lake oxygen levels mapped out over a year or two, you could probably re-sell your meter on Pond Boss and only take a small loss.

For pond pH a pet shop pH kit would do all you need to have done for your pond goals. pH in your type of water is pretty stable and usually only has big changes when alkalinity is low below 30-40mg/L. See the very good article in Current PBoss Mag Jul-Aug by Dr Boyd about alkalinity.

WIPondGuy, I second what Bill is saying. But I understand you not wanting to sell as well. So, here's what I'd recommend.

1) Buy the YSI O2 meter. An optical meter will allow you to get O2 readings faster than one that takes a membrane such as the YSI-55.
2) You can take a water sample and send it off for testing. That's one of the things that we do for our customers, even long distance customers. You can do a number of tests yourself, but things like nutrient levels, pesticide or heavy metal testing has to be done in a lab.
3) Know going into this that it won't be cheap, and that be prepared to bear the brunt of the costs if ALL the homeowners don't have the same goals for the water as you do. Even though other people will benefit, not all want to share the costs.