Pond Boss Forums AERATION Systems questions Aerator Iced and Snowed Over

I live in western Iowa and like most of the Midwest we are in a subzero cold wave. I have a bottom aerator on one end of my oval-shaped 1 acre 16t deep pond (the shallower end) that I run all winter long. The whole pond is now frozen over and covered in snow. The aerator is still running but I cannot see any open area above it. I'm guessing the pond will stay frozen and snow covered for quite a long time now. My question is should I turn the aerator off? It's my understanding that if a frozen pond is not snow covered some sunlight will penetrate and that will help generate some oxygen...true? However with it being snow covered that's not going to happen. My obvious concern is over-oxygenating the water and killing fish.

So, should I turn off the aerator and just leave it off, or put it on a timer and only run it for a certain amount of time every day? Or should I leave it on and auger a couple holes in the ice to allow excess oxygen to escape? Augering holes would be easiest at the opposite end of the pond off my dock about 70 yards from the aerator. Thanks for your input.

First some questions:
How much snow is on the pond?

Are there any spots where wind has moved snow off the ice - I call these spots wind blown areas?

How long has it been snow covered with over 2" of snow on top of the ice?

How thick is the ice?

Average depth of the pond?

For the acre of water estimate the percentage of water over 12ft deep.

About 4-6 inches of snow on ice.

The pond is completely covered, no bare spots.

Snow has been there for 5 days now.

I apologize but I do not know how thick the ice is, I've never augered a hole in it (pond is 3 years old). I can only say that in the past I've been hesitant to walk out on it. If I had to guess I'd say 5 inches with this very cold weather.

Average depth estimate 8ft

12ft percentage 1/4.

Just FYI fish species are walleye (up to 16"), yellow perch (up to 11"), and some large hybrid blue gill. Aerator is bottom double membrane diffuser, placed at one end of pond in about 6' of water.

1. 5" of snow cover on clear ice allows only 1-3% of the light to enter the water under the ice. Plant DO production needs to have 10%-12% of light on the ice cover to produce dissolved oxygen (DO).

2. Your 3 yr old Pond is considered new in terms of the life of the pond. This means the amount of dead organic accumulation on the bottom is low and with bottom aeration a lot of the organic sludge has been decomposed due to well oxygenated bottom water circulation from the bottom aeration. The lack of bottom muck means the oxygen will last a lot longer during the ice and snow covered conditions compared to a pond that is 12 to 20 years old. As the pond ages to 10+ years be more concerned about winterkill. My estimate the DO on the bottom of the deep basin of your current newish 3 yr old pond should last at least 4-5 weeks with complete snow cover before you should be concerned about a fish kill. If lots of tree leaves entered the pond in fall then DO could become in short supply by 3 weeks of snow cover in your new pond. Old dead organic rich ponds are the one most prone to winter kill. Because ice freeze up was late this year around Jan 1 the harsh winter will not last as long as prior years so IMO chances of winter kill is low for states in the Iowa latitude.

3. 25% of the pond at 12ft deep means more water volume to hold more DO that in a newish pond should add another 2 weeks of good DO for a total of 5-6 maybe 8 weeks before water column DO is lost. Remember every living thing during winter water is 39F water from 2ft deep to the bottom. This means all bacteria to the biggest critters are basically dormant and they use very little DO. Ponds freezing up have 11-13 ppm DO which means it takes lots of weeks of respiration from bacteria to fish to use up all the DO in 8-12 ft of water column

4. If you are overly concerned and with the aerator turn it off for several days of ice forming temps, then IMO you should auger a hole about 3-7 ft from shore. Then restart the aerator to allow the air to escape and the dissolved gasses if present in the water to escape. If you do not trust walking on the ice, auger holes 1 -2 ft apart to very the ice thickness as you move away from shore. 4" of ice is plenty of thickness to hold you up. I walk and fish on 3" of ice. A guy this week ran a snowmobile on 6" of ice no problem.

5. My way of checking the amount of DO during ice and snow cover is to go ice fishing in the deepest part of the pond. Put the baited lure 6"-12" from the bottom. If you can catch a fish at 11-12 ft deep there is good DO on the bottom zone of a 12 ft deep pond. When the DO is lost during ice - snow cover DO is first lost on the bottom and then very gradually and slowly DO loss works its way up toward the ice bottom layer. This takes numerous weeks during the 39F water temps not days as DO can be lose during warm water of summer. 12feet is a long depth of water column to loose DO in winter.

6. A January or February thaw or a rain should usually occur in a typical Iowa winter. This often melts most of the snow when snow is less than 10"-14" thick. Then With melted snow down to some bare ice, light again enters the ice for DO production. then we just wait for all snow and ice to melt.

Thanks for the awesome reply and information, very interesting. Just want to make sure I understand one thing. With the blizzard conditions we have experienced I am not yet able to get to my pond to turn off the aerator. Since it is frozen over and snow covered how concerned should I be about over-saturation of DO? Is there a point in time where it becomes an issue for fish? Should I get to it as soon as possible and turn off the aerator, and then look at drilling a couple holes in the ice, then turn it back on. I can drill holes right off the end of my dock, where I can check to keep them open.

Using ambient air you will NEVER see an over saturation of O2. The extra air will find a way to get out of the pond, even if it means sliding under the ice to the edge of the pond at the shoreline.

Commander:

Chill (pun intended).

1. You don't really need to run aeration in the Winter once the water temp gets below 50 deg F or so if the pond is open. Water holds a heck of a lot of O2 at low temps, and fish metabolism has slowed way down (hence their O2 demand is low). E.G., large mouth bass metabolism drops by 50% with every 8 deg F that the water temp drops - other species have a great metabolism drop with lower temps too;.

2. If the pond gets covered with snowy ice (so no sunlight penetrates), you start counting how long it's been. Since you have a pretty new pond, I estimate you have at least 2 weeks before you need to worry about low O2. Cody, who knows more about ponds that I ever will, says you've got longer than that. With my 22 year old pond that has been heavily fed its entire life (and is therefore full of organic material to decay and consume O2 under snowy ice cover), I go a week before worrying about having low O2 (successfully).

3. I am surprised that your aerator 6 feet down hasn't melted a hole through the ice already. But when you have counted snow cover long enough to worry, then turn on the aeration and let it A) add O2 under the ice and draw bad decomp gases off as they exit the (presumably) edges of the pond with all the excess air you're adding and B) eventually melt a hole through the ice. FWIW the shallow aeration sources in my two ponds that I use for icehole opening are at roughly 4 ft and 6 ft.

4. Excessive Winter aeration when unneeded carries the risk of super cooling the pond water to the possible detriment of warm water species (which, with no RES, you don't really have). This occurs since the warmest water in a frozen over pond is down on the bottom at 39 deg F (which is the temp at which water is the densest) is carried up to the surface by aeration where it cools to 32 deg. With your aeration at only 6 feet down, you still have a warm (well, 39 deg F) refuge in the deeper parts of the pond that your fish can use if they choose to. I doubt your constant Winter aeration actually poses much of a super cooling threat (due to 6 ft aeration placement and cool water species), but its most likely not needed and wastes electricity while putting run hours on your compressor.

So, chill.

Since we are supposed to be in a warming trend for the next 20 days, and I have an open area in the pond, I shut off my aerator.