I was talking with a fisheries biologist the other day who stated the following:

"In northern climates I don't recommend winter aeration. The reason for this is that solar energy is absorbed by the dark colored bottom of the pond. Combined with plant and bacterial activity this creates a band of warmer, denser,heavier water on the bottom which is between 36-39 degrees. If you are aerating when the air temperature is less than zero degrees F. you can "supercool" the water that's been brought to the surface to slightly below freezing. This water is then returned to the pond by circulation and you can end up losing this band of warm water that fish such as bluegills and bass like to inhabit. Since cold water in the presence of a healthy plant and algae population is likely to be already high in oxygen why would you bother to use the electricity necessary to aerate a pond in the winter"?

I thought this was an interesting viewpoint, which is probably only applicable to smaller ponds in the northern part of the U.S. and Canada. Does anyone have any comments on this or do you think it's much ado about nothing? I do realize that thick ice covered with several inches of snow can be a contributor to winterkill situations. That notwithstanding the biologist seemed to have a valid argument.

I think the key is not to put your air stones in the deepest water... thus avoiding much disruption of any potential 'warmer' water.

Without an open air hole to allow gases to escape there is always a risk of them reaching toxic levels during the winter.

I don't recall the last time I saw ice that was clear enough to allow significant amounts of light penetration... at least not enough to replace the oxygen created by 'anchored' plant life with oxygen created by the various free-floating algae.

I know for sure that without aeration I would have zero game fish left at the end of the winter... the longer the winter the more likely of a big kill from lack of oxygen or poor water quality. With rooted plant decay and very little light penetration I can pretty much guarantee my fish would die without aeration. They benefit not only from the oxygen added to the water by the 'bubbles', but by the open area that then allows light penetration and gas escape.

I don't recall the last time I saw ice that was clear enough to allow significant amounts of light penetration... at least not enough to replace the oxygen created by 'anchored' plant life with oxygen created by the various free-floating algae. I can clear some areas of snow but that still leaves at least 18-24 inches of 'patch-work' ice that doesn't pass light worth a darn.

I like the way you think, Pottsy.

I'm sure that our friendly Texan pondmeisters are having a good laugh at our expense right about now.

Are you suggesting that I could get the best of both worlds by setting up my stones maybe two or three feet off of the bottom?

Small northern ponds also benefit from the warming effect of the ground, that's why heat pumps work with buried coils, they take advantage of the latent heat in the ground. I would agree with Pottsy that the best of both worlds is to raise the aeration up to the shallower depths to keep open a clear window for photosynthesis, but if airflow is reduced so the mixing is not excessive with deeper bottom diffusion membranes, the water will gain heat from the ground and not stay at the supercooled temperatures. The trick is to strike a balance between natural warming at depth and circulating too much supercooled water. My vote is to keep the oxygen saturated at depth and that means aeration.

PaPond, I've been reading your posts and I really enjoy the way you present your ideas. Do you have a background in limnology? It sure seems like it.

I'm casting you my highest rating! I hope you're around for a long time because this forum really benefits from viewpoints like yours.

Bruce

I would like to hear more opinions. I turn off my aerator for the winter months. The only fish kill stories that I have ever heard occurred during the hotter months - (or possibly a lake turnover in the spring or fall). I figure that if oxygen was a problem in the winter months, then there would be a lot dead fish in the 10,000 Natural lakes in Minnesota. Any other Pondbosses have an oxygen related fishkill occur during the winter? Is this rare or common?

Bruce, why thank you, I don't believe I've ever been rated before, been berated often but never rated. I do have a background in oceanography, my masters is in chemical oceanography and I specialized in marsh nutrient systems. This sweetwater stuff is all new to me. When I finished grad school back in '74 jobs in oceanography were few and far between, now I'm reading Pond Boss and I hear about all these guys who went the fresh water route, from Texas no less! Very encouraging.

Interesting topic, and one of the few that I actually have "some" experience with. I think one of the major factors involved here is the fish density of your pond and also the pond's age and amount of nutrient present. The larger the b.o.d. (biological oxygen demand) then the greater chance of some winterkill.As an advantage, colder water holds more oxygen than warm water.
I only have experience with trout, where a warm water refuge is not really an issue for survival so I cannot comment on the pros, cons of that.
Last winter I had 196 days of ice on my pond. Maximum ice thickness was over 30". I did not aerate and had no winterkill at all. This is a newer pond and fairly low density. I did remove most snow cover quickly and routinely.
The one thing I found that did suprise me was the amount of light penetration through very thick ice. Dropping the underwater camera down even with only 6" of snow cover showed almost complete darkness, yet where I kept the snow off was very well illuminated all the way to bottom even with near 3 foot ice thickness. For my purposes, snow removal is key to over wintering trout and not aeration.
Oh, and for you Texans, air temps this morning here were -37c. Tonight when I got home we were at -4c. Gotta like the Rocky Mountains.
Wood

The worst experience ever with my pond was right after the first winter. We stocked it the first summer with yellow perch, LMB, and hybrid bluegills. By fall we had bass that here 10-12". We left the aerator in the deepest spot on the advice of the pro that sold us the fish and the equipment. All winter we couldn't wait to see the fish in the spring. When the ice receded there were dead fish everywhere. The bass died first and were badly decomposed. The bluegills were completely gone. The yellow perch survived for the most part but were badly stressed. Some of them you could grab out with your hand but they were still alive.

That summer we were blessed with a swarm of baby bullheads and no predators to control them. (they don't show up till mid summer when it is too hot to stock bass). We had algae like you wouldn't beleive from all the nutrients. The water smelled terrible.

We restocked the bass the following spring and caught 362 bulheads by hook and line and trapping. I am starting to regain the balance after 2 years.

Ever since then I have place my airstone in about 3 feet of water. I tie it to a post on my dock. I did not lose any fish last year and hope not to lose any this year. Plus the open water lets me keep my dock in all winter. The song birds like having the open water by the dock also.

To end a long story, do not deep water aerate through the winter in cold climates. I move mine in the fall when the water gets down into the low 50's (around Haloween) and will put it in the deep area once the surface gets over 50 and still I am careful to check the temps every day.

Be careful.
Brian

Great topic, and one on which I am NOT an expert. However, I am quickly learning by hard experience. I had a few comments that I thought might add to this discussion.

First, I want to ensure that winter aeration is given credit for being a useful technique. When you get sufficiently long winters with sufficiently productive water bodies, there is no way to sustain a fish community without aeration. So, this does NOT apply everywhere, but certainly does in the northern plains states (eastern SD is a good example). There is no way that a 3-acre pond, even 15 feet deep, would sustain a pond fish community through the winter in my locale without some assistance.

Before I continue, I must admit to knowing way too little about winter aeration. I was always taught and passed on the old idea that you put the aerator discharge into the deepest part of a water body. Heck, it made sense! The warmest water is at the bottom of the pond during the winter because water is heaviest at 39 F (4 C). [Without this very unique characteristic, ponds would freeze from the bottom up rather than the top down, and we’d really be in trouble! :-)] So, it made sense to me that you put the air bubbles into the warmest water, and then lifted that water to melt a hole in the ice above. This little factoid obviously was not correct! I also was always taught that direct transfer of oxygen from the air bubbles to the water was minimal. The open hole in the ice allows some photosynthesis and oxygen production, even from the reduced algal/plant community in winter. This little factoid apparently is correct, although I recently learned that direct transfer of oxygen also occurs from the atmosphere to the open-water surface.

The concept that winter aerators should be placed in shallow water has been a great example of how I have learned much from this forum. Let me pass on my “mistake” story.

We had two ponds, one 3 acres and one 7 acres. Both were in grassed watersheds, both were relatively deep (18 ft and 23 ft, respectively), and both were moderately productive, but not overly so. They were far from electricity, so Koender’s windmills were installed, and we put the airstones on the bottom in the deepest part of the pond. The winter of 2000/2001 was a tough one that started early, and ran late. We had snow and ice in October, and so much snow that the ice did not blow clear. Ice-out did not occur until the start of April. What a sad day that was. I walked the shorelines of both ponds, and it was hard to see all those dead 12 inch black crappies that we had developed in the largemouth bass pond. It was similarly hard to look at all those 18 inch smallmouth bass dead on the shoreline of the smallmouth-only pond. The aerators had worked well all winter. During calm periods, the open hole in the ice would freeze over, but as long as there was wind, the holes would open. By the way, a 22-acre pond with 3 windmills survived that bad winter in great shape.

I was sorely disappointed in these winterkills because the ponds were built as well as possible, in as good a watershed as they could be, and the aerators were installed. Based on good input from this Forum, I learned that during a long winter period of circulation, the aeration may result in cooling of the entire water body (under the ice). Too long at too cold temps may stress the fish too much. I also learned that too much aeration may circulate too much water, and allow too much of this cooling to occur. So this lesson is simple: don’t use more aeration than necessary for the size of your water body. There are people on this website far more qualified than I to provide information on appropriate air volume capabilities for various sizes of ponds.

So, what did we do at those two ponds? Well, I suggested to the landowner that he move the aerators up into shallow water, just as has been suggested here.

One of the Pond Boss Forum regulars passed on a publication to me. Theron G. Miller and W. C. Mackay, 2003, Optimizing artificial aeration for lake winterkill prevention, Lake and Reservoir Management, Volume 19, number 4, pages 355-363. I learned a lot from this article, and it certainly fits with the concepts expressed so far on this topic. In this study in Alberta, they found that dissolved oxygen levels actually were better in waters with surface aerators (kept a hole open in the ice) than from aeration units in which the airstone was on the lake bottom. The key was keeping that hole open in the ice. Circulating from the bottom up apparently must have moved some organic material, because dissolved oxygen was always lower in waters with those circulation systems. Finally, this paper actually had some recommendations on optimal sizes of aeration units, based on kW per unit of surface area for the water body.

This may sound funny, but I think we need some more field assessment of aeration and winterkill potential. This winter, I was hoping to get dissolved oxygen profiles from several of the area ponds we manage (ponds with windmill aerators, and some gravel/sand pits that don’t have and don’t need aeration). However, it’s already Dec 10, and there is only a skim of ice on the ponds due to this warm fall we are having. So, it will be a short winter this year! I’m not sure how much we will learn. Good old Mother Nature and her variability!

Dave

Bruce -- who was the biologist to whom you were talking? This person apparently knows the subject matter, and I'd like to talk with him/her.

Thanks,
Dave

Dave Willis, very interesting reading. Concerning your post on the fish kill in the 2 ponds I was curious if you did an DO reading anytime that winter. Was wondering if the kill was more DO deprived than water temperature related. Here is the reasoning. If you had ice/snow cover for 6 months that is a long time for DO to be sustained at any favorable level. The Koender with a 7-8 inch round airstone even in 20 ft of water at a full 1.5 CFM (I belive 1CFM is closer) and figuring 1000 GPM turnover would mean that the 7 acre pond using an average depth of only 15 ft would need 24 days to tunover 1 time. This turnover rate would have no effect on water temp to speak of.

Part 2, (Sorry about the dual posts)My experience in NW Ohio has been that winter aeration with ice cover is needed very little.I monitor my DO level with a YSI DO meter all winter long, Last year for example the ice was clear most of the time and I think this is the key. I had 14 inches of ice most of the winter and never had less than 103% of saturation and a lot of 110% or 12-14 PPM DO 38-42F and would be content with 5-7 ppm .However I will open up my winter diffuser which is a Koender Airstone with 1 cfm of air for the 2-3 days that it takes to punch a hole in the ice if I have a lot of snow cover. I always recommend a placement of this stone in 3 ft of water.One of my personal ponds is only 2 years old and was filled with well water 1.1 acre (pic at www.cleanponds.com)my smaller pond is 4/10 acre and has 38 acres of ag watershed and is 40 plus years old.(pond on the the right in pic)This pond has a Koender windmill and the standard stone in it for winter aeration and had the same DO levels all winter. The airstone in this pond was left at the 8 ft level last year but probably only turns 300-400 GPM at that level.It did not keep open water much and had water temps in the bottom (8 ft) of about 37-38 F, so not much temp decrease due to over circulation.All ponds seem to winter differently. If DO levels are checked you can access the need to aerate or not.Letting some light in still seems to be the safest way to boost DO levels for those of us in the North.I have more concern about a aeration system that can turn the entire water column over 1-2 times per day than windmill that circulate far less than that.If you monitor your DO levels in the ponds with the airstones either electric or wind powered and they are not acceptable considering doing some research on diffuser selection. Ted

Dave,

The biologist's name is Aaron Klusmire who is the head fisheries biologist for Natural Habitats Unlimited. He says he was taught by a possible acquaintance of yours named Chris Guy at Kansas State University. If you wish to speak with him his phone number is 402-672-6191. Aaron's help has been invaluable to me over the last several years (and he's a pretty good guy, too). He has been involved in some pretty amazing trout habitat undertakings in Wyoming.

Ted: Very good points. Thank you!! That is good advice. To answer your question, no, we did not have d.o. measurements. As I mentioned earlier, I need to know more about this topic, and we are planning some monitoring this winter. When the 3-acre pond killed, there was a distinct hydrogen sulfide smell that is typical of the winterkills around here. I know from visiting with an Ohio DNR biologist in Findlay that you folks have one heck of a lot milder winters than we do. Thus, it sure sounds like a person should think twice before undertaking winter aeration. Honestly, though, we’ve got waters that would never sustain a fish community without some open water. Winterkill is a fact of life here, in both public waters and small private waters. Bottom line: we’ll monitor d.o. this winter, and then maybe we can at least ask the right questions! As you indicated, we don’t even know the root cause of the problem right now.

Bruce: Thanks for the biologist update. I appreciate it. Yes, Chris Guy was actually my first PhD student. He’s a gem. However, Aaron learned about aeration systems somewhere/somehow that did not involve me!! :-)

Dave

I've learned about winter aeration from the school of hard knocks too. Some bad advice out there and sometimes people sell you stuff but don't tell you anything. I too aerated in the deepest water with not one but two diffusers my first winter! More is better right? I didn't have a fish kill probably because the pond was so new, but my bass were definintely stressed come spring and some of the biggest ones succumbed to some kind of pathogen, I'm assuming, because their immune system was compromised by the stress. After I stopped that stupidity my fish have come into spring just fine ever since.

I have found here in northern Indiana if you can keep the snow off for the most part you don't need any aeration. However I set up a diffuser in shallow water with a small compressor just in case we get lots of snow before the ice gets very thick. If your ice isn't very thick yet, and you get lots of snow you're screwed if you want to get the snow off the ice. And the gas release thing causes me to crank it up when air temps are above freezing to open up a hole now and then. I do have a really high density of feed trained bass so I may run the shallow diffuer all winter to be on the safe side. I do run a small one in shallow water on the trout pond all winter.

I use a snow blower on my .62 acre pond and believe me the pond looks really big when you have to blow the snow off. However I believe if you take it off in strips you're O.K.

For the one from Missouri --how much ice do you get in Missouri? I know you get an occasional snowstorm, but I would think if your ice doesn't last more than a month you shoudn't have to aerate if you can keep the snow off.

So far a mild winter here too. Had skim ice a couple times on the small trout pond and only once on the bigger warmwater fish pond. But we usually dont' get good ice until around Christmas.

Cecil,

You're assumption about Missouri is correct. I live in NW Missouri and we rarely have ice for extended periods of time. Last year we had about a three week time period with 6" of ice. Overall, I would say that the ice period is highly variable even for us up in the colder parts of the state. Four years ago we had 18" of ice for nearly 1 month. Three years ago we didn't have enough ice to get out and fish. It's just not that predictable here. The longest I have ever seen the lakes locked up is 9 weeks.

We are, however, subject to winter-related fish kills. Trust me. My phone rings off the hook after ice out. Most of these ponds are highly fertile, shallow, and overstocked as you would figure. I give the same advice as others have already posted, keep windows open by removing snow. Our bigger, state managed lakes will occassionally have mild kills.....mostly shad. This is my favorite time to fish for channel cats using shad sides and shad guts:)

Pondbosses - Thanks for all the replies regarding winter pond aeration. Very interesting subject. I would gladly pay for winter aeration costs, if I knew it was required. (I wish the O2 analyzers were not so expensive.)
Sounds like more fish are killed by deep water aeration mistakes than if there was no aeration at all.
I do not think anyone has yet posted that they actually measured low dissolved oxygen levels in the winter. Several people have reported winter fishkills, low O2 was assumed, but was it proven by actual measurement??
I would be very interested in winter O2 data reports, especially in the worst case conditions, high fish density, frozen lake with snow, no aeration.
Many Thanks!

These are really some great posts, I belive some fish will survive the winter because of it !!Yes I agree the DO meters are costly but such a great tool.Perhaps we can get Bill Cody to wade in on this subject some more as Bill has commented on it before (see prior posts)I think everyone agrees that the least one can do is try to get some snow off in strips if on the ice for more than a month.But as Cecil commented if you get an inch of ice and 4 inches of snow you have a problem !!

Caution!!: Non-scientific comment to follow!

It seems intuitively correct that organisms that are made up of almost all water would favor a little temperature gap from freezing. A fish has a hard enough time fighting off everything else without fighting crystalization of it's slime layer. (Sure, I'm exaggerating, but 39 F. sounds a lot more comfortable than 34 F.) Very, very interesting the previous comment from Brian Loberger about losing his Centrarchidae but having his yellow perch survive. Perch are a true cool water fish, especially compared to bluegill and largemouth which are a little more warm water/fringe fish from an evolutionary standpoint. Could it be that perch, walleye and trout could withstand "supercooling" just a little better?

Again, no data to support this...just a little theoretical guessing.

Bruce,

I know the trout can as I have run an aerator in deep water in the trout pond with no problems. Could be the the walleye and perch are more tolerant, but it could also be they can handle lower D.O. or a little of both. Trout cannot handle low D.O. very well in most circumstances.

Believe it or not aquaculturists and academics around here are referring to largemouth now as "coolwater" fish. It was not so when I studied fisheries. If you think about it they are a coolwater fish ih contrast to catfish and talapia which have higher optimum temps. I see the AFS now considers the Florida largemouth a different species than the northern largemouth due to DNA analyisis.

If fish can be stressed by the supercooling of the deeper water by aeration, then how do cage culture fish fare when they are essentially trapped in a pen close (within 5 feet) to the surface, where theoretically the water is the coldest. Are there different guidelines for aeration if you're floating a cage of trout or HSB in a northern pond? Since water starts its natural migration to the surface at 39 degrees, and reaches the surface when it is at or very close to 32, the surface waters must be pretty nippy for the caged fish. Are they stressed similarly to the fish supercooled by bottom aeration over the winter?

PaPond, Bruce, Wood, Pottsy Cecil and others; Please educate me. I'm in Texas and, around here, ice is something that is usually manufactured and water doesn't often get down to 39 degrees except on the edge of a body of water. Your post says that water rises at 39 degrees and real obviously freezes in your part of the world when it gets to the surface. By itself, that makes sense.

However, my ignorance is why the cooler water doesn't sink. I am assuming (dangerous, I know) that water, like air, rises when warmed and falls when cooled. That is why the bottom of my pond is cooler than the top and,to some degree, why we have thermoclines. Now, there is something real basic here that I don't understand. If that rule were always true, ice would be on the bottom of the pond. I realize that statement is an exaggeration and assume that air trapped in freezing water keeps it more buoyant. It seems that 33 degree water would flee from the surface to always be replaced by warmer water. I guess it also begs the question of why water "layers" as in a thermocline. Surface water temp is obviously influenced by air temp. It appears that water should constantly be mixing and a thermocline shouldn't exist. Thanks in advance for answers that most Texans have never had a reason to ponder.

Hey Wood, we have a cold front or what we call a Norther coming in tonight. The temp will plummet about 25 degrees to the 50'sF during the day and will get down to freezing during the early morning. Sure hope it doesn't last long.

Water is the densest at 39 deg F (4 deg C). It's been a long time since college Physics & Chemistry, but I will try to remember enough to give a better explanation than "Just because."
Liquid water is just that, a liquid. There is no structure between any of the water molecules and their spacing, while much tighter than in the gaseous state (steam), is controlled by how much energy they have and therefore how fast they are moving. The energy is the temperature; the warmer the water, the more energy the molecules have, the faster they move, the farther apart they are. Warmer water means less dense (lighter in weight).
Colder water means less energy, slower molecules, tighter spacing, more dense (heavier in weight). So normally the colder (heavy) water sinks and the warmer (lighter) water rises, which causes the normal Summer temperature gradient that may be seen all year round down South where "Ice" comes out of the freezer.
But when water gets cold enough, it freezes. Ice is a solid, which means the water molecules in it are rigidly locked into position. They have to be lined up in those 60 & 120 degree angle formations that make the characteristic 6 sided figures we know as snowflakes.
Now comes the tricky part. Liquid water doesn't freeze into a solid until it's temperature drops to 32 deg F. But when the water temperature gets below 39 deg F, the molecules start to form up into the 60 degree angle formations. They don't actually get all the way there until 32 deg F, but they start to line up, kind like being tied together with bungee cord as opposed to being rigidly glued together like they will be once they're ice. This semi-structure forces the water molecules farther apart than they were just above 39 deg F, overpowering the closing-up effect that lowering temperature was having on molecule energy and spacing.
So from high temperatures down to 39 deg F, cooling water packs it's molecules tighter and makes it denser. Below 39 deg F, (partial) molecule structure overcomes the energy loss packing, and the molecules grow farther part, making the water less dense. At 32 deg F ice forms, which is less dense (lighter) than water, so it floats. This gives the (northern) winter temperature gradient with the densest, warmest (39 deg F) water on the bottom, the lighter, colder (32-39 deg F) water above that, and the lightest stuff (ice) on top.
If this weird condition didn't occur and ice sank, not only would your pond freeze from the bottom (as pointed out above), the oceans would, too. Studies have shown that they would also stay frozen except for a meltwater layer on top, tying up most of the planet's water and making life on Earth very different, if not impossible.
If there's a real (or just better) physics guy on the forum, you can straighten this out, but that's how I remember it.

Dave, The one thing we all have in common in our ponds is the water, and water acts in a very unique way. Generally water sinks the cooler it gets, and thats true up north as well, the catch is that at 39 or 40 degrees the density of water begins to change, the molecules begin to line up for the formation of ice and in the process become less dense. The closer to freezing it gets the closer they are aligned into what will become the chrystalline structure we all call ice. The alignment process is (or was when I was in college) called the 'pseudo chrystalline state' But think about it, if water didn't behave that way, life as we know it might not be here. Ponds would freeze from the bottom up and a lowly pond is where the whole thing probably started. The fact that water behaves this way, allows the ponds to get a stir, mix the nutrient soup up a bit, and bring the life back in the spring. But then again maybe life began in Texas where the ponds don't freeze and that's why you guys get such big ponds!

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

RobertB, My understanding is that all biological processes involve liberation of heat energy so I'm sure you're correct in your "composting" suggestion.

Russ, I'm glad nobody thought of your idea when I was in school. I might still be in graduate studies.

Russ/Bruce: Now I'll have to decide between the dark brews and the light domestic brews. Which will most motivate?? Questions, questions, questions.

Dave

Dave,

Dark or light domestic....you're getting into the deep water now. Since I don't drink, I'll have to step aside and let someone else toss you the life preserver.
:p

Russ

After reading through this thread and using my personal experiences of this past winter, it is readily apparent that clearing the snow off of the ice is extremely important to the survival of fish populations in smaller ponds.

My pond is 2/3 the size of a hockey rink and has a max depth of 25'. I cleared the snow off for pond hockey every winter and noted that one or two bass has died off, in seven years. This past winter was crummy with heavy snowfall followed by freezing rain and slushy conditions that made the chore of clearing the pond less than appealing. Couple that with the risk of taking the new heavier snow-thrower on thin ice and a general laziness on my part... well, it just didn't happen, OKAY! Sorry.

You can guess the rest of the story, I am sure. We were horrified to find a complete annihilation of our beloved smallmouth bass. Not one survived. My son and I counted 42 fish floating or visible on the incline around the sides. How many were on the bottom out of view?

My name is AZ, and I am a fish killer. I am here to get help.

We drag the diffuser into the area around the overflow just to keep it open when the pond freezes.The swans and geese and deer seem to appreciate it; we haven't lost any fish to date but if anyone thinks the HSB would prefer no aeration in my zone this winter, please let me know.

I see that AZ has found this thread just like I just did. AZ you asked some questions on another thread about this subject and I replied with my limited experience. This appears to be the place to be. As I indicated in that thread I was aware of the issue with super cooling and with the belief that fish were also unable to absorb oxygen if they were stuck in water that was too cold. That is what an expert told me. Whatever the case is I have been successful with HBG, LMB, and crappie in my 1/2 acre pond with bottom air stone diffuser (deepest part of pond) that runs as much as possible in winter to keep the DO level up but not so much as to drive the water temperature too cold. It appears putting the aerator in the deepest area might be a mistake but its worked so far. My rationale was to avoid stratification and give the fish more area to live in. I keep thinking that one of these days something I've done wrong will catch up to me and I'll lose everything but I can't bring myself to change something that's been working. I can't afford a DO meter so I calculated the size of pump and number of stones required to result in a DO much higher than my calculated BOD.

Hope you guys don't mind me interrupting your technical discussion with a funny story about winter aeration? I just gotta tell this to somebody! Last winter I figured it would be kind of fun to experiment to see how long it took to open a hole in the ice with the aerator. So I turned the air pump off one evening so that the pond could freeze over night. The next day I had about 4 inches of ice over the whole pond. My pond is oval shaped. I turned the aerator on that morning to see how fast I could melt a hole. There was no snow on the iced and the ice was crystal clear. To my surprise before the moving water under the ice could melt a hole the ice lifted up off the water. I let the pump run for about 6 hours and it continued to blow up my pond. The ice lifted up over a foot above the water like a big balloon, my air gage said I had 5 psi under the ice. I kept thinking it would eventually break. It didn't melt cause the water bubbling upward no longer touched the ice. This went on until the entire pond all the way to the edges had a ice dome over it. I finally got tired of waiting for it to break so I got the 22 rifle. One shot in the middle of the pond and the whole thing exploded into a million pieces. It broke so violently that I got all wet standing by the pond. When my wife asked what happened I told her I "blew up the pond". She's still confused. Should start a thread on pond stories.

bz - did you get a picture of the ice dome?. Home video would have been even better; it might have got you on a TV show.

Bill, wish I had a picture. Now that I think about it I must have had the aerator running all day cause I started it in the morning and didn't blow the think until after dark. I have a yard light shining on the pond but that wasn't enough for a picture. If I had known it was going to be such a show I would have at least tried. Always wanted to send something to Funniest Home Videos. Had another incident last winter where pond froze over despite the aerator, -20 F will do that. It took a shotgun slug to break through this time but is wasn't good solid clear ice so it didn't shatter. When the ice dome dopped back down onto the water a geyser shot up out of the 3 inch hole and got me right in the face from about 15 feet away.

bz - This winter's ice follies may provide material for some pictures.

I got my airstone moved to shallow (3' or 4') water today for the Winter, for the first time. I should have done it last weekend; we had 1" of ice on the pond the day after Thanksgiving, which fortunately had almost all melted today. Water temps were 40.0 deg F at the surface and 39.6 deg F on the bottom.

My wife assisted from shore and came up with the great idea of floating the 5 gallon bucket with gravel and the airstone using (swimming pool) noodles. I could fit 3 noodles through the handle on the bucket which provided plenty of floatation, making the job much, much nicer to accomplish from a canoe.

Re Aeration: Have 1 acre pond, 15 yrs old, stocked for 4 years in E. Central Ia. The 1st 3 years after stocking simply put a large round bale in at shore edge before freezeup. Had no problems with winterkill. Did not break ice nor remove snow. Last year I got "professional" and installed a 1/2 horse Gast "fin" pump, 1/2" tube and stainless steel diffuser in deep water. Created a 15-20' hole in 8" of ice all winter. This spring I had fish kill (LMB, HBG, couple of CC). Needless to say I now have a cheap big bale of grasshay at the pond edge. We'll see what happens come spring. Thanks-Postbeetle.

Thakns for the information, postbeetle! Quite a few of us are trying to better understand winter aeration. Did you have your airstone/diffuser in the deepest water in your pond?

Well Postbettle from my experience you over did it. I did the same with two airlines in deepwater a few years ago with a 1/3 hp compressor. I had a partial fish kill too come spring along with stressed bass.

I now use a much smaller compressor and airflow to the lip edge of the ponds. No more than three feet deep. I believe I could get away with no air flow if I keep snow of the ponds (do that too), but the problem is there is always a chance you could get thin ice with a heavy snowfall and not be able to get on the ice to remove the snow. I also go to Florida to visit the folks a few weeks in December every other year, and don't want to take the chance of heavy snowfall while I'm away.

I'm going to set up my smaller compressors and airlines today.

Dave :

I just revisited this post and was interested in an update on the status of the ponds that were in the works from last Dec. Were they built, how many, size, cost , use , etc.?

Ewest -- I assume you are referring to the research ponds? No progress on that topic whatsoever! However, we definitely hit a cold spell here after a nice, long, warm fall. So, I probably need to start thinking about some D.O. profiles on a couple of the ponds. I'll bet we can get out on some ice soon. The 7-day forecast calls for below-normal temperatures.

post, I believe Cecil has your answer as to what may have gone wrong.Winter aeration can be quite simple and complicated at the same time. When trying to find and maintain the balance of a high percentage of DO saturation and water temps not stressful or lethal to fish without a DO meter it is difficult.I find most winter aeration overdone in the midwest.When your BOD is very high winter aeration is more critical and with a low BOD it may not be needed at all.When in doubt and no way to tell the DO level just keep the snow off of at least 20% of the surface and chances are you will be fine. This is my preferred method. Next method is to have a seperate diffuser (or move your exsisting one) to the shallows and only run when snow cover is present and only as long as it takes to melt off an open area and them let refreeze clear.On ponds where multiple diffusers are present shutting down the majority of them and using one designated as the winter diffuser works too. Caution if you have more CFM going to that one diffuser than it can handle.Either vent off so that you have 1-2 PSI going to that diffuser or install a diffuser that can handle variable CFM (look at the AirPod from Aeration Technologies Inc) as it can take from .5 to 10 CFM.Lastly if you have your only diffuser in the deeper part of the pond and cant move it and cant install a seperate winter diffuser then consider at least venting off most of the air to it, say 1-2 PSI and slow it down. The idea of large open water so a pond can gass off often supercools the bottom of small ponds (8-10 acres and less) and does more harm than good.Winter is already the tough time for fish and over circulation only makes things worse.Most 40F water that is 80-90 % saturated has 10-12 ppm DO in it already and that is twice as much O2 as you need this time of year.Many of todays diffusers can circulate over 4000 GPM with only 1 cfm (20 ft of water)and your pump may have over 4 cfm available.Since proper winter aeration differs so much from year to year I would stay on the conservative side in a small pond.If you have 20 ft or less depth in a 1 acre pond and have open water all winter from aeration and air temps single digits and below you probably have your bottom water too cold (less than 39F) If you have one or two diffusers (depending on depth) running in a 8-10 acre pond all winter probably will not cause any problems as its the smaller ponds that are the most difficult to manage.Use the ice to your advanage as insulation against the super cold temps. Good Luck.