Pond Boss Forums INTRO Questions & Observations Aeration "Supercooling"

PaPond

Could it be that what we're really talking about here is a two-pronged issue. True--aeration will cool a small pond the way that stirring your coffee in a duck blind will speed the cooling process. The amount of cooling depends on the ratio of stirring (size of your aeration system) to water volume (size of your pond). A properly sized aerator, as noted by Ted Lea, probably doesn't have much impact. Anyway, the second issue could be suspension of bottom silt, detritus and waste created by a poorly placed winter aeration system. This would likely further inhibit light movement through your water column, resulting in less phytoplankton production and the subsequent reduction in available oxygen. Excessive cooling + suspended crud + less oxygen = more stress.

How's that for sloppy science??

Theo,

My Grandpa raised cattle and he told me the following:

"There's only two types of cattle ranchers--smart ranchers and ex-ranchers."

Thanks for the answer. I'm saving that one.

PaPond,

From someone that's been doing seasonal cage culture for several years and overwintered caged fish one winter I can give you some information based on experience. I've have also included a website that covers cage culture in depth that talks about overwintering fish if you can find the right link. Don't remember which exact link it is at the present time but here is the website:

http://aquanic.org/beginer/systems/cages.htm

I don't overwinter fish in a floating cage unless I have to as it IS stressful on them and can be risky where one gets ice cover. Typically folks that overwinter fish in cages do so in climes where their ponds don't freeze over. Additionally since their ponds do not freeze over, but the water gets fairly cold, lack of oxygen and too cold of water are not an issue as it would be with ice and snow cover and much colder temps. In fact, they are able to hold more fish (trout) per cubic foot because of this increased oxygen level. I have also observed no ill effect to mixing of the water column to trout when I have done it. In fact I actually fed them in the open water caused buy the diffuser! Since the metabolism of the trout is still active in water in these southern climes, the trout can be continued to be fed and this is conducive to good health and optimum growth. No experience with hybrid striped bass.

From a past experience overwintering feed trained smallmouth fingerlings (was only able to purchase them in the fall) I would suggest if you have to overwinter fish in a cage, cover the cage with the same material the cage is made out of, and suspend the cage a foot of two off the bottom. The first year I tried to overwinter smallmouth in a cage, the cage actually sunk below the surface from the weight of ice build up, and most of the smallmouth escaped because I left the cage on surface.

I am presently overwintering another batch of 200 smallmouth fingerlings in one 7 X 7 foot cage and about 350 bluegills in another 7 X 7 foot cage. The smallmouth are too small to release into the pond with several hundred over 8 inches to 20 inch feed trained largemouths as they would be decimated. The bluegill I want to sex come late spring and plant only the males in a small pond I had recently dug. Hence protecting the feeding them in the floating cages.

What I have done is after securing the top of the cage with the same material the sides are made of so the fish cannot escape, I have attached two strands of nylon rope about three feet long to a couple of ajacent corners of the cage and to the other end of each of these ropes two floats (orange juice or detergent or mineral spirit gallon jugs). On the other opposing side of the cage are two more nylon ropes of the appropriate length attached to my pier. Once the jugs are removed that were originally attached to the cage to keep the top of the cage above water, the cages sinks until the ropes stop it's progress. (I have drilled holes in the PVC frames when originally constructed to allow the PVC to fill with water which causes them to sink evenly) Since the water depth there is 9 feet and the cage bottom where the fish reside is 4 feet, (cage is 4 feet high) by sinking the tops of the cages top 3 feet below the water surface the fish are residing 7 feet down at 2 feet off the bottom.This should allow them to overwinter O.K. and I will let anyone know of the results if they are interested.

I will NOT aerate anywhere near the cages as I want them to have a somewhat warmer water refuge. I may aerate very close to shore in a shallow end of the pond though due to my large density of bass in the pond.

Thanks all, after reading everything about 3 times I kinda get it about 39 F being the magic number where molecular change really starts hustling and, I guess, stops or shuts down around 32 F. Or, at least, everything gets lined up and peaceful at 32 F.

Boy, I don't think life started in Texas. But I kinda figure that the heavy duty immigration prior to the Battle of the Alamo and other stuff had something to do with the discovery of Tequila.

Actually, the size of West Texas water holes is a variable. Due to sparse rainfall, hot temps, low humidity and heavy evaporation, a one acre stock tank (pond) in May can become a half acre by the end of August. I get pretty narrow minded about fertilization with biomass problems under those conditions.

This has been an informative post, it has prompted me to follow Potsy's lead and shut down my Vertex aeration system which is in the deeper portion because it consumes $1.40 a day in electricity (609.5 watts) and it isn't doing the pond much good. I'll replace it with an Airtech pump from an old Koi pond that pumps 47 liters per minute (approx 1.65cu ft /min) at 6 1/2 feet depth and only uses 47 watts (11.2 cents a day) and place it by my dock so I don't have to pull it out and I'll have a win win situation. I won't have to take out the floating dock, I'll keep the ice open for O2 exchange, and I'll spend alot less on electric.
Dave, So am I correct in assuming that a good portion of the ponds in Texas do not have feeder streams that run all or most of the time? If that's the case we should re-open a former post asking the difference between a lake and a pond to ask the difference between a pond and a puddle?

PaPond, Few West Texas ponds, that I am aware of, are on actual waterways. I can't really speak for East Texas but believe it to be about the same way. Quite a few that I know of are on seasonal creeks. For the most part, we stop up gulleys and impound runoff. I occasionally hear of small creeks being stopped up with coffer dams to build an actual dam but not often unless it's a government project of some kind.

On the other hand, there is only one natural lake in Texas. It is Lake Caddo. All other lakes result in stopping up rivers and good sized creeks. Most are also used for power generation and domestic use. Most are used for city water supply.

As I alluded to earlier, the difference in a pond and a puddle just might depend on the time of the year.

I worked on this answer for a couple days. Post was enhanced again on Dec 13th.

This discussion of winter aeration has been interesting.

Bruce brings up the phenomonon of super-cooling of the entire water column during ice cover when diffusers are operated in the deep pond basin. Pottsy reports that his experiences lead him to believe that thicker ice is not clear enough to allow penetration of adequate light to maintain photosynthesis for plants to enhance the pond’s dissolved oxygen. PaPond remarks that the geo-thermal affect also aids the warming of the water near the mud water interface. Wood’s experiences lead him to believe that fish density, pond age, overall nutrient content and BOD of the pond are important in whether a pond needs aerated. D.Willis reminds us that oxygen transfers into water from diffused air bubbles and when the unfrozen open water area is exposed to atmospheric air. Ted provides some information about his DO and temperature measurements during ice cover and experiments of diffuser types and their location or placement. Brian, Dave and Cecil reported their experiences of the affects of supercooling on their fish.

Here are my experiences and homework results on this topic:
My temperature tests have proven that deep water mixing from aeration does lower the temperature below the normal 39F in the overall water column i.e. super-cooling or chilling. I have measured temperatures of 34F-36F through much of the water column and near the bottom even in a pond where the aerator was shut off a week or two before ice formed. Extended aeration and wind action supercooled the water in this situation before ice formation.

The warm water layer near the pond bottom is due primarily to the transmission or release of heat that was absorbed by the sediments during the warm periods of the year (Wetzel 1983, 2001). Geothermal affect has been measured to occur but is a low amount compared to the overall release of the summer heat sink from the sediments. I think the amount of heat release from the sediments can be even greater during winter when the pond has been aerated to a point during the summer where the water column is a fairly uniform temperature top to bottom (homoiothermic). I have measured aerated bottom water to be 80F+ during summer. I think this condition allows a greater amount of heat to be absorbed by sediments and then it is transmitted or releaed back to the water during winter. In these homiothermic ponds I have measured bottom water temperatures of as high as 41F to 41.4F during ice cover; truly a warm water refuge during winter.


In almost all cases, I think aeration is not needed during winter. McComas 2003 recommends about 30% of the ice surface can be cleared of snow cover and it can be removed in alternating strips of snow strip, clear strip, snow strip , clear strip. As a rule I try to not let snow cover the ice more than 7 to 10 days before I remove some of it. I usually try to remove the snow in north-south strips to take advantage of the angle of sunlight penetration through the ice. I am not sure if this is a more effective method, but I do it just in case. Often many of the wind exposed ponds in NW OH get fairly large areas cleared of snow by blowing wind and snow shoveling is not necessary.

Light stimulates underwater plants to produce oxygen that dissolves into the water. Three main types of underwater plants – phytoplankton, attached algae, and rooted submerged “weeds”, produce the majority of the dissolved oxygen (DO) in ponds and lakes. Light penetration through ice cover is very important in maintaining dissolved oxygen (DO) levels during winter. Light will pass through clear ice similar to that through water (Wetzel (2001). However the condition or type of ice and snow cover can greatly affect the amount of light that penetrates the ice cover. Snow cover reduces light penetration through ice the most. Snow at 5” deep stops about all light transmission through ice. Cloudy surface ice layer, white ice or ice with air bubles has an intermediate light transmission affect. When light can shine through 17” of clear ice about 72% of light will pass through and 23% will pass through 5 ft of clear ice (Wetzel 2001). This was verified by Wood when he kept snow off his Alberta pond with up to 37” of ice and his trout survived the extended ice cover season without aeration. Trout require at least 5 ppm DO for survival. Phytoplankton under the ice did their job of producing adequate DO all winter long for Wood and his trout pond.

I have noticed that ice will freeze very clear even in relatively cloudy water that was murky from suspended solid particulates. When I chop ice holes for fishing in a pond with fairly cloudy water, the lower chunks of ice are composed of very clear ice that look like glass. It looks very similar to ice made from distilled water – very clear. I think this occurs because as ice crystals form it forces the particulates away from the forming ice crystals and the ice forms clear. This clear ice allows lots of light transmission.

DO has been measured to increase about 3 ppm per day for 3 days under snow free ice due mostly to activity of phytoplankton (Bennett 1970). The high saturation of DO that Ted Lea measured under ice was no doubt due to phytoplankton activity under the ice. Certain phytoplankton taxa or forms have a survival advantage to thrive in cold water with low light intensities (Wetzel 2001). Some algae types have been reported to actually form bloom conditions under the ice. More research will provide more information in these areas. I think that the cold water species of phytoplankton which are usually composed of very small forms can do an excellent job of producing DO, especially during sunny days, if they get a small amount of light though the surface ice cover.

Alternatively, in extreme cases DO has been measured to decrease very rapidly under ice cover in a Michigan lake where DO decreased from 12.3 ppm to 2.4 ppm in 2 days (5ppm/day). Normally DO loss is not normally this rapid when a fresh snow blankets the ice cover. Some lakes can withstand several weeks to a several months of snow covered ice conditions and still have adequate DO for fish survival. The primary cause of DO loss in winter is due to the amount of microbial activity and decomposition of organic particulates in the water column and organic sediments (BOD biochemical oxygen demand).

Obviously the more organically enriched and shallower the water body the more rapid the loss of DO will be in the dark conditions under snow covered ice. Keep in mind that in dark conditions, everything living consumes oxygen including bacteria decomposing the already dead materials. When conditions have been dark long enough that the plants die or begin to deteriorate and then illuminated conditions reoccur there will be a lag or delay time for plants to either recolonize, reestablish or recover before substantial oxygen production can begin again.

If removing snow from ice is not economically or physically feasible then use of aeration can be an option for enhancing the DO of a pond or small lake. If DO levels in WINTER cold water drop to 2 or 1ppm or less the pond has a potential for winter kill and aeration at that point in time will probably not prevent winterkill for that year. Fish will tolerate lower DO in winter than summer due to a lower metabolism. Too little - too late. The intent is not to oxygenate the entire lake or pond but rather create an oxygen rich refuge in part of the lake to allow fish to survive the low oxygen periods under ice and snow cover. The goal of winter aeration should be to aerate 10% of the lake volume to minimize the chance of winter kill (McComas 2003).

Fish Cages Froze in Ice. I routinely allow my floating fish cages to freeze in ice cover. My cages are 32" to 40" deep from the water surface. My fish appear to be in good shape when the ice thaws in spring. Occassionaly I have drilled holes in the ice and dropped sinking food in the cage and watched fish eat sinking food. When I looked at my old water temperature measurements during ice cover the water at 3 ft deep ranged from 39F to 39.2F.

I will do more temperature measurements this winter to get a more detailed profile of the water temperatures just below the ice down to 5 ft deep. I will also measure the bottom water heating affect at various depths.

Bill,

Could be my cages had ice build up etc. due to their size (at least 7 X 7) and I did have a diffuser running in the vicinity that first year.

I still feel safer dropping them down into a warmer layer, and I probably have a higher amount of fish than you do. About 350 five to seven inch bluegills right now in one of those 7 X 7 cages and 200 SMB in another 7 X 7 cage.

We'll see how they come out come spring.

Hi folks. I have one more “tangent” to toss into this discussion. My thought was stimulated by Bruce C.’s earlier suggestion that coolwater or coldwater fish might be more able to tolerate extended, colder water periods during winter (his example was 34 F vs. 39 F) than are warmwater fishes. This certainly is possible, and it sounds probable based on the experiences reported here. In addition, tolerance for low levels of dissolved oxygen (DO) varies among fish species.

One of the “toughest” fish when it comes to surviving low DO is actually the fathead minnow. They survive when there is almost no measurable oxygen in the water. Fishes such as northern pike and the yellow perch are also more tolerant of low DO than most other fishes. Fishes such as black crappies, largemouth bass, and bluegill will die before the yellow perch and northern pike as DO declines over winter.

Shallow, marshy, productive lakes in the north country often have pretty simple fish communities because they tend to have DO problems under ice cover. So, such waters often contain northern pike, yellow perch, fathead minnows, and black bullheads (low DO tolerant species) rather than walleye or black crappie that require more DO for winter survival.

Cecil made the point that a combination of factors likely stress fish and induce winterkill, and I’m sure he is right on target. The cooler temperatures likely add stress. The low DO obviously can add stress. Then, I wonder if some of the decomposition gasses that accumulate under the ice, such as hydrogen sulfide and methane, might add another stress. As I mentioned earlier, it may sound silly, but we don’t know everything that we should know about winterkill!

Dave

Bill Cody, you quoted from Wetzel that certain taxa of algae exhibit higher ability to survive and even bloom in cold conditions and even under ice. If these algae strains don't go absolutely wild in warmer conditions and take over a pond, they might be valuable to innoculate a pond with right at the time of fall overturn. Their increased numbers could possibly provide a 'low tech' oxygenation of the iced over pond, again, providing they wouldn't take over in the warmer months. Do you have more specific species names for these alga? It would be interesting to read up on their requirements. It would be very cool to be able to buy a culture of algae to innoculate a pond with to insure oxygen saturation sans electricity.

PaPond - It is extremely rare and difficult for cold water algae types to grow in conditions of summer. It is very doubtful that you would need to innoculate your pond with some of these cool or cold-water algae types. Most ponds, especially northern ponds, have an abundant, natural mixture of species that grow and decline with seasonal cycles. It's hard to beat "mother nature's" design and resoursefullness. The current ambient and competitive conditions determine whether they start reproducing or not and how much reproduction takes place. It's sort of like growth of cancer cells in the human body; dormant until something triggers growth. The algae cells do not all "die" when the population declines or crashes. Many types just "hang out" as rare individuals, dormant cells or some have special resting stages or forms. These forms can then revive when conditions are "right" for regrowth and reproduction.

The only ponds that would benefit from algae inoculations or seedings would be those that have been subjected to repetitive herbicide treatments which tend to, in the long term, deminish the natural and diverse algal community of ponds.

A note for D. Willis. Dave if you are planning some studies of aeration of ponds maybe you can include in your winter aeration studies a pond that has a portion of the snow removed compared to a simlar control pond where no snow is removed. That would be interesting data. I would be willing to analyse several whole water samples from the ponds for phytoplankton composition and density for no charge.

Bill,

I raked out a bunch of Chara this fall from the trout pond. You should see the mossy deep green filatmentous algae that is taking it's place. It's really prolific and it really surprises me in this cold of water!

Cecil - That mossy green filamentous algae with survive all winter long under ice and will produce DO if it gets adequate light.

In small, productive and fertile ponds that have prolonged periods of full ice coverage, what types of gasses build up in the absence of an aeration system?

I'm aware that the nitrogen cycle, which results in nitrification of unionized ammonia provides for some loss of nitrogen gas to the air/water interface. Are there other gasses such as hydrogen sulfide (briefly mentioned by Dave Willis) that are produced by pond muck that need to be released to the atmosphere during the winter in eutrophic ponds? Or are these sediments better left undisturbed during the winter months?

Bill – thanks for your kind offer! Thanks also for your practical suggestions. If we are going to do it, do it right, eh?? It would indeed be interesting to monitor oxygen in a pond with only snow removed. I’m not sure if I have one to do that, but “surely” could find one.

My initial thought on some winter research actually has me a little worried. What I need is a graduate student who can accomplish all this work. I’m afraid that I don’t have personal time for a thorough project, such as the one you envision. Maybe my next step better see if I can convince any funding agency that we need to do this work. It’s expensive to maintain a graduate student these days. However, that is one way to ensure a thorough job! I do have one current graduate student who was willing to run the temp/dissolved oxygen profiles this winter, but he has another project that takes most of his time. I doubt whether snow removal will fit into his schedule. Let me chew on this a while, and thanks again!

It’s been cold the past two nights, so we are actually making some ice. However, the forecast is for highs in the 40s for the next week or so.

Dave

This is a very interesting topic. I am having a 1 acre pond built that will be only about 10 feet deep, possibly a little more in small areas. I am concerned about problems with winter kill.
This may be a stupid question but if the cause of the winterkill is decreased DO and the biggest way to prevent a decrease in DO is to get light to the plants so that they can produce oxygen, why not place a light or lights in the pond under the ice? I realize this would require electricity but so does aeration (unless you're using a windmill) but unlike aeration it seems to me instead of supercooling the water a light would have the potential to also provide a small amount of heat so that there would be at least a small area for the fish that would have a more favorable tempurature for them which would decrease another stress upon them.
Like I said this may be a dumb question but I had to ask.

I guess I started this topic by talking with Bruce about potential "supercooling" of smaller (less than 5 acres)pond and lakes by aerating in the deepest part of the lake. I aerate several smaller lakes in NW Wyoming at about 8000 feet. 8-10 feet of snowfall and average temps of less than zero for 6-8 weeks. We had a landowner who reintroduced a pair of Trumpter swans on to one of his lakes. The lake was 3 surface acres, with a max depth of 16 feet. The only fish in the lake were Snake river cutthroat trout which had winter killed the year before. We set up a 1/2 horsepower system with two diffusers in the 15-16 foot deep range. We managed to keep an area in the lake open about 50 X 50 feet all winter. The swans survived, but we killed every trout in the lake. He has 3 other ponds, in which we put the diffusers in .5 x max depth. We did not lose a trout in the 3 ponds. We also work on a larger pond about 20 acres in size. In this pond, which had winter killed every year for as long as anyone could remember, we put four diffusers, run off two 1/3 horsepower pumps in the deepest part of the lake 13-14 feet. The reason we did this was the aquatic vegetation was prevalent in water less than 8 feet deep and the lake had been stocked with several thousand pounds of trout that summer. I felt it was worth the supercooling risk because of the BOD problem I knew we were going to encounter. We have not lost a fish in that lake in 3 years and now have rainbow trout over 7 pounds. I belive the size of this lake is the only reason it has not super cooled. I aerate several lakes in southeast NE and how I set up the systems depends on several conditions, but I have yet to have a fish kill because of super cooling. My point is if you are going to aerate, consult someone from your region, don't let someone in Florida design a aeration system for a farm pond in Iowa.

My pond is in north ID. about1/2 acre. When the pond froze over last winter all my trout were killed off. I won't put any fish bk. in till i get air into the water for the winter, only way to go if u want to keep your fish alive

Aaron - I think that aerating only a portion of a larger body of water like recommended by McComas 2003 i.e.10% and similar to what you seem to be doing provides a transition zone from higher to lower of oxygen and temperature. The fish can seek an area that at least meets their minimal needs for survival. When small water bodies are aerated too much or to strongly the transition zone between high and low is eliminated and the fish have to tolerate the prevailing conditions; no refuge areas are available.

Bruce C. The two main anaerobic decompositional harmful gasses are hydrgen sulfide and methane. Hydrogen sulfide is very water soluable and toxic to fish at very low levels which I am sure you know. H2S to fish is similar to carbon monoxide to humans. Decompositional carbon dioxide should not acumulate to levels that are toxic to fish, plus the plants will absorb most of this if they get light. Decompositonal hydrogen gas should be very reactive and bind with available ions to form other compounds.

Dave W. I thought the upper level and graduate student's main purpose in school was for slave labor. It always seemed that way when I was in school. Things have no doubt changed since I was in graduate school. Any way to make this class project for fisheries or limnology class? What you need are several 1/10 to 1/2 acre research ponds. Students shoveling snow instead of drinking beer, what a concept! It probably would never catch on in today's world.

TO ALL READERS IN THE NORTH. To see the importance of removing some of the snow from the ice in winter see the post and testimony of Ability Zone on July 22 2005 below.

Yes, Bill, you'd be a real comedian on campus these days. :-)

You are also EXACTLY right about the small research ponds -- we really need them. We have been working for years to get them, and just can't get the funding. We even found a location north of campus. The university foundation is currently looking for funds for pond construction. All I can do is keep my fingers crossed.

At the least, I will at least get some temperature and oxygen profiles this winter. Maybe more extensive work can be undertaken next year with a little more advance planning. Just to get to the three locations at which I would have ponds to monitor would take about an 80-mile loop each time. So, this isn't something to undertake lightly. With this mild winter so far, it may not have been a good "test" year anyhow. In mild winters, we often get 12-14 inches of ice. In long, hard winters, I've seen 30-36 inches of ice cover.

Thanks for the continued good suggestions. Appreciate it.

Dave

The concept of the sediments releasing stored heat is an interesting one. Has anyone ever seen a thermal heat cycle made up for bodies of water. the general one showing stratification and ice cover leaves out the sediments. I would imagine that "composting" of the organics on the bottom would add to this stored heat.
Robert B

Dave,

After freeze up and before snowfall, scatter a cache of brew around the pond. Tell the students, you want it, you dig for it.......no metal detectors allowed.

Russ

Dave--Maybe I'm just biased, but it seems like the economic impact of winterkill on smaller, public waters alone justifies the expense of the study. You'd think the monies would be available for something this important!

I hope it works out for next year. If one of my ponds can be used in any way to help with this sort of research let me know.

Bruce