Pond Boss Forums INTRO Questions & Observations Moving Aerator in Winter?

I just added a windmill aerator to my pond. The pond is approx. 1/2 acre 12-14ft. max depth. A friend that has a pond said that I should move the aerator from the deep part of the pond to an area 4-5ft deep for the winter. That way it still keeps some open water area when the pond freezes, but it keep the deep water from turning over and helps it stay a little warmer in the deeper water.
The place that I bought the aerator from said that I should keep the bubbler in in the deepest part of the pond all year.
What should I do ?????
Thanks in advance for any advice.....

Your friend is correct. Fish need a warm water refuge in the winter. By putting it in the deepest water in the winter this takes this refuge away. Go with your friends advice and forget about the retailer he is flat wrong.

Jeff

fins - To be completely fair to all advisors, I think you should take the time to pose this question back to the retailer and mention to them the warm water refuge concept of winter aeration. Retailer may have a common sense reason/opinion for leaving the diffuser in the deepest water all winter. Please, Come back and give us HIS OPINION or rebuttal.
For reference, also Tell me where you bought your windmill.

As far as I know this warm water winter refuge concept primarily pertains to electric air compressor driven systems. My Rational or Theory::: Most, but not all, electric systems move a lot more water than the windmill units. They also move the water stronger and farther. Amount or percentage of water in the pond moved is a function of 1. the amount or volume air produced, 2. size of the diffuser, 3. size of the pond 4. shape of the pond basin and 5. depth of the diffuser/diffusers.

Movement of lots of water during winter in small ponds such as yours will pump all the water out of the pond bottom, decrease its temperature below 39F at the surface and remix this colder water back to the bottom. The pond becomes completely mixed and few if any areas are unmixed. The colder the temperature of surface air and the longer the system runs continues to lower the overall pond water temperature. I have tested or measured this condition several times.

Any temperature below 39F for the fish is an additional stress that would not have occurred if the aerator was not operated in winter. Even operation of the diffuser in shallow water causes significiant mixing of the pond water under the ice cover. This was tested at Cecil Baird's pond in winter of 2002 when his bass showed signs of red gums or teeth areas.

The more stress applied to your fish the more susceptable they are to disease. Your fish (depending on species present) will be able to tolerate some lowering of their body temperature but to what degree?? This will depend on lots of variables. Some tolerate cold water better than others. Chronic cold water conditions below 39 to 40F are a lot worse on the overall fish's health than an occassional foray into colder water.

Back to my theory... The windmill is a comparatively sporatic and weak water mixer. Thus it may?? not cause undue temperature reduction stress to your fish. I have not tested the water temperature reduction affects produced by the windmill during winter; Maybe I can get that done this winter. Where in OH do you live?

My retailer suggested I leave my electric powered aerator in the deep water all winter also. I lost ton's of fish my first winter. I have not seen a bass or bluegill all summer. The yellow perch were stressed when the ice went out and we lost sum, but the bass and bluegill clearly died much earlier in the winter. Especially the large ones. The retailer said this could not have anything to do with leaving the aerator deep and he had never had a loss like that before. We are in Wisconsin and it was very cold last winter.

He referred me to a fish vetrinarian at the state level and he agreed that the aeration overmixing the water would have caused it. I plan on suspending the stone a foot or two below the surface and off to one side. This was suggested my the fish vet and by Cecil from his experience also. I will probably just secure it to a dock post. I leave my dock in all year.

At what time of year or at what water temp should I pull it off the bottom ans suspend it ?

Brian

in winter,i put mine on rock pile bout 3 ft below in the shallow end ,the deep water one is shut off. from what i have read and learned, you want keep some do moving , keep ice open for gases, let some sun into the water for the plants and leave the deep part alone. it's mother nature's way to protect the fish from winter, the refuge of 50 or so degree of water in the winter in the deepest part of the pond.

I live in west central Ohio - Auglaize Co.
I realize the windmill will not move as much water as the electric aeration systems, but there is no electric near the pond site, and I feel that whatever water the windmill moves is better than nothing at all.
I plan on moving the aerator into a shallow area of the pond 3-4 ft on one end this winter.
What time of the year should I move it and when should I put it back in the deep water?

You are correct, the w.mill is a whole lot better than no aeration at all. I've seen windmill aerators produce complete summer mixing in some ponds and not others. Several things affect the degree of mixing. It is possible that windmill mixing under the ice could throughly mix the pond especially if it is windy where the windmuil sits during the winter.

Since you are in west central OH is assume you got your w.mill from JL Becker. I would not trust much of what he says about fish & aeration unless he agrees to back fish deaths up with replacments. He is a contractor by trade not a fisheries person or someone with a biology background. He deals with heresay, stories, opinions and tests verifies little if anything about ponds.

Q1. Is your diffuser the 6" dia stone or a 10" dia rubber membrane? Membrane will mix at least twice more water per hour.

In central OH, move your diffuser shallower around Halloween or in early November. Replace it to deep water no later than May 20, but better in mid to late April or first week of May.
If your pond is deep +12', (which it is) not old and fairly clean bottomed (sludge and weedy) and you keep 1 & or 2 week old snow off 25% of the ice you do not need to run the aerator. winter running can cause mechanical problems if the diffser check valve is not working properly.

Q2. Do you have a presure relief valve in the airline?

All this talk about winter aeration has me confused. My pond is 1/3 to ½ acre in size and slightly peanut shaped. It is 10 ft. deep on one end and 12 ft. deep on the other end. (that is during full conditions. I am down about 12” – 18” at the moment.). I have the gast ¼ hp air compressor from Stoney Creek with (2) rubber membrane diffusers located in the both ends of the pond. Originally I was going to shut off one end and leave the other end going but now I am concerned about doing that reading these posts about shallow water diffusion during the winter. I do have one area where the bottom is a little more gradually sloped on the extreme end of the pond where I could maybe put a diffuser in about 8 ft of water.

Questions are:

1. Do I shut off one and leave the other diffuser running?
2. Do I disconnect both and add a third diffuser along the edge in 8ft. of water?
3. Do I shut them all off?
4. How do you start up in the spring and when? Right now the diffusers are running 24/7.

I should mention this is a new pond, dug last November. It was stocked with bass, bluegill, catfish and perch. I should also mention that my kids love Ice Skating but boy does it make me nervous. With the amount of neighbor kids that come over I am always afraid of someone falling thru! Should also mention this is in Southeast michigan near Flint. One other question. I have the ability to raise the water by garden hose (6" in three days of full flow 24hours a day). Should I do it or leave it till spring?

No just a check valve at the airstone.

fins: I also don't put much confidence in Mescan's overall knowledge about ponds. They sell equipment and that's about all you should expect from them (only my opinion). As an example, he is not even setting up or advising you about your mill properly to run trouble free in the winter during ice forming conditions.

If you don't have a freeze control and OR without the pressure relief option in winter expect trouble eventually. Maybe not this winter but it will happen in a winter in the future. REASON. All check valves underwater eventually fail or clog. When your underwater check valve fails & the wind stops, water will fill all airline underwater and a freeze plug will form at the water line the thickness of the current ice conditons. When the wind resumes pressure will build until the weakest point breakes. We have had some crank shafts even fracture. The freeze control injection mechanism is not real dependable in the long term. A pressure relief valve with a low pressure setting will prevent all these problems if they try to occcur. Plan to clean your airstone every year or two in muraic acid. All difusers clog over time. Clog time depends on numerous factors.

f.bear - Do you use Aquashade that limits oxygen production??

If you are going to be ice skating /sleding on your pond I would not run your aaerator in winter because:
1. You have a new pond. New ponds have very little oxygen demand/loss in the winter under ice. Your depth should have a "storehouse" supply of oxygen for a minimum of 5 weeks in total darkness under snow cover.

2. Since your kids will be skating or playing on ice someone will shovel at least some of the snow off (mimimum 20%) . Wind may also blow a sizable spot clean of snow. This will allow light peneteration then phytoplankton will make all the oxygen needed during winter. Sporaic short term 3 wk snow cover is not real bad in YOUR situation. However 12" to 18" of snow cover for 5 -7 wks is bad. If around Flint you get 6" to 12" snow cover on ice ALL winter I would consider running aerator at the shallow depth (4'-5') maybe beach area daily 4- 6 hrs thru winter. Just enough to keep an open area near shore for light penetration.

3. If you insist on running a diffuser in winter pull one of them into 4ft deep and run it there 5 to 6 hrs per day. Make sure your check valve is working good before freeze up and that you have pressure relief on the compressor if you turn it of periodically. Same reason as with "fins" windmill above.

4. Resume aeration in spring when surface water temp is 46 to 55F.

Running 24/7 I would love to supply you guys with repair parts for your compressor. Most all my customers run only 4 to 6 hrs per day in a pond like yours. They don't need any parts until 7 to 10 years. Running 24/7 you will replace vanes or rebuild kit is due in 10000 hrs. You do the math.

Bill,

I did use aquashade early in the year and have not replenished it yet and also don't plan on it. The way the pump is set up it would be hard to shut it off on a daily basis. I wish I would of know that last spring when I installed everything. The one thing about runnning the aerator 24/7 is that it does keep the top of the pond looking nice and my wife likes it, so keeping the peace might be worth the rebuild kit every 10,000 hours or so.

On average the units that we run get vane replacements after 3-4 years. We run across some problems with starting and stopping motors since the metals in the compressors contract and expand differently than the carbon vanes. This seems to shatter them sometimes. Also, I wonder about in temperature extremes how fast the water can re-stratify and develope an anoxic layer to kill the present bacteria? Any more thoughts on this?
Robert B

Vane replacement can occur less frequently than every 10000 hrs if the compessor does not have to pressurize at 10psi. If the pump runs at 5 psi the vanes will last longer maybe 20,000 hrs. Also dirty air filters hasten vane deterioration.

Some compressors that had Emerson motors had occassional start switch problems, but never any problems with GE motors. Moist operating environment can also be a problem for starting and stopping some compressors esp those poorly housed.
For the last ten years we have not had very much trouble with starting and restarting GAST compressors providing the compressors are maintained and operated properly. Most pondowners are not told about the proper running conditions for the pump. Sellers usually spend a minimal time with the buyer and the buyer leaves nieve about pump care & operation. Often buyers get units from mail order and instrucions for compressor care is almost nonexistant from these sellers.

Shattering of vanes sounds to me like the occurrence of a spike of excessive pressure. This can occur under several certain conditions. This is the only reason we see shattered vanes. It is not due directly to starting and stopping, but maybe indirectly, esp if simple preventative items have not been installed or maintained.

I think that metals & carbon expanding and contracting differently within the compresssor are very likely not the cause of shattered vanes. Was this confirmed by an engineer at GAST?

I'm not sure what you consider temperature extremes for re-stratify. The amount of restratification of the surface layer that can occur in one day is not a big problem, as I have seen it at least in many places in the USA outside hot desert areas. Even in those areas, I doubt it would be a major problem. BOD is the primary cause of oxygen loss in the deep zone and surface sediment areas. To compensate for this possible problem, most of the aeration distributors in my area have pondowners run their units twice a day for 2 to 4 hours each time. Some will run three times a day for various periods or once a day. I can make a convincing argument for doing it either way so it probably doesn't make a lot of difference at least in most ponds in our area of the country -northern midwest. Exceptions can occur (see next paragraph) but they are not the typical or normal pond.

I have tested oxygen loss rate in restratified ponds. It is variable but the pond has to be almost a sewage pond before oxygen at 6 to 8 mg/l (ppm) is consumed down to below 3ppm within 24 hours at the bottom in the restraified zone or newly formed hypolimnion. Another exception would during a plankton bloom crash which causes a bacterial bloom which consumes DO very fast.

Invertebrates will probably be the first to go in the upper sediment when the pond restratifies. Fish will be first "to go" in the pelagic areas when oxygen is depleated from the deep zone. Since aerobic bacteria are fairly low oxygen tolerant they will likely be last to die as the zone turns to anoxic. Anoxic conditons first occur at the mud water interface. In fact with continual aeration 24/7 the bottom is warmed more than if the system were run for a shorter period. With warmer bottom sediments from 24/7 operation the oxygen will be lost quicker at the mud water interface due to greater bacterial/invertebrate activity. However this can be a positive if rapid sediment consumption is a goal.

Thanks for the info Bill. I'm pretty sure the vane breaking reasoning did come from Gast a few years ago. I assume in your last paragraph you mean aerobic bacteria. With our management practices we do sometimes deal with the near sewage lagoon. Years of direct agricultural runoff, or ponds dug in peat bogs are too common. This along with the augmentation usually biweekly of bacteria makes continual operation sensical. There is such a wide range of practices with aeration dependent on so many variables and experiences among installers. With high BOD, we shoot for theoretical complete mixing 3-4 times a day. Using gast pumps or blowers and Mix Air diffusers, this can be easily accomplished. Our independant test data on the bladder diffusers or stones that we've been given makes me wonder what kind of turnover rates someone can get by running for only a percentage of the day. However, the desired end result of bottom DO levels above 1ppm are usually the base requirements for a system, but if bacterial colonization is at depth zero and DO isn't maintained even a few centimeters off bottom, this would slow or stop decomposition. I know when we drop a DO meter down, we may not be reading at this exact of a distance. We try to adopt the wastewater concept in our management practices, of course to a much less concentrated extent. Hopefully I've made sense, and this stirs some other info sharing and experiences. Throwing algaecides, dyes, and other things into the mix keeps things interesting. I like to keep an open mind on any subject, and have picked up alot of info on this site, it's not just for new pond owners,although I often refer clients here if they are computer literate.
Robert B fishmgr@hotmail.com

RobertB - Yes. I fixed the bacteria thing above; proof reading error. As you mention, ponds with high BOB do require more water movement to minimize oxygen drops to the low levels. In our area we deal with mostly ponds less than 1 acre and fairly new systems which typically have relatively low overall BOD. Organic rich, shaded ponds, and large ponds do require different aeration periods.

Turnover rates are basically determined by testing. Theory often carries little weight here.

In my understanding of organic sediment decompositon, the invertebrates such as midge larvae, nematodes and oligochates play a very big part in the deep water detritus processing. All these guys also require DO levels at the mud sediment interface. Bacteria are responsible for the final stages of decay to chemical products; DOC's (dissolved organic carbon) and other complex by products..

Did your shatttered vanes occur mostly in cold weather or winter? I will call an engineer that helps me with problems at Gast Mfg next week and report back.

Over the last four years I may have come across about 4-5 shattered sets. Most seem to be in the summer. Sometimes only one vane gets broke, but usually debris will break a few more or all. Have you ever used a different style of compressor? I have seen the worm screw type, but not in action. Vanes, pistons, and blowers with a few diaphrams are all that I've used. It's nice to get different viewpoints on management practices.
Robert B

I talked with an engineer at GAST mfg. He said metals expanding differently is not the cause for vane shattering. He said all the metal and carbon vane expansion has been taken into account in the engineering and design of the rotary vane units. He said vane shatering is most likely due to foreign matter in the vane cavity (improper air filtration) or over pressurization. He said vane shattering often occurs soon after a rapair job or rebuilding which results in "dirt" in the rotar cavity to cause vane shatter.

I am not aware of the worm screw type units.