Pond Boss Forums Thread Like Summary - Aerator Causing Poor Ice Quality?

Hello everyone,

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

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

Any advice or comments would be appreciated.

Thank you.

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

For starting an aerator under firm ice, I auger a hole above the aerator and turn in on. Air escapes through the hole and upwelling 39F water and bubbling action erodes the ice fairly quickly depending on ice thickness. .

Here is an update for everyone.

We tried running the aerator on a timer but the stopping and starting of the aerator caused condensation in the line to freeze and cause issues, so we are just running it full time now. Our ice is more than thick enough at this point in the winter, so having it run full time does not seem to be an issue. I was fishing about 30 feet or so from the edge of the open area and the ice was 14" thick.

I have not even seen a brown trout while I've been fishing. I've only seen and caught rainbows. I have no idea where the browns go in the winter but they become next to impossible to locate or catch. The rainbows seem very healthy and have lots of isopods in their stomachs which appear to be keeping them well fed. Any mixing of the water that the aerator is doing does not seem to be making the rainbows any less aggressive. I don't know how the (unwanted) bass are fairing though.

Thanks again for all of the advice.

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

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

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

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

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

Turn off the aerator.

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

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

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

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

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



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

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

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

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

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

Fyfer - you should see my post on aerating in similar conditions to you. I have my diffusers suspended from a pipe for the winter so as not to mix the entire water column. To minimize or possibly negate the effect of the aeration on ice quality you could easily build a floating frame that was attached to the pipe with the pipe in the center. Fix it so that the aeration plume comes up in the center of the floating frame. Voila, you have best of both worlds. You should be able to run aeration 24/7 in the winter and walk right up to the edge of your floating frame. I know a guy in MN that does this very thing. He can ice fish in his aeration hole. Of course being a Candadian I am sure you are well versed on ice safety, but full disclaimer anyway- make sure your installation is solid and working properly and ice is safe before you ever attempted walking anywhere near an aeration hole.

When I did a ice thickness test on my pond, the ice didn't change thickness until I was within 30 feet of the open water from the diffuser.