Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Snow removal over ice

Are there any studies on what percent of the snow cover needs to be removed over ice to prevent a fish kill? I know that every situation is different, but we will have over 6 inches of snow over ice for the foreseeable future and I am wondering if clearing a 10' x 10 area on a 1 acre pond will have any real effect? Guessing that a lot of ponds are in the same boat.

Seems like it couldn't hurt and might help sort of situation. Clear an even bigger area and get out the skates!

Not an expert, but I doubt 10'x10' would create any significant benefit.

How thick is your ice?

Can you put a jon boat with a gas motor onto the pond and "ice breaker" the pond so the snow falls through?

Is the snow still fluffy such that you can blast some clear patches with a powerful leaf blower?

Finally, if you are only going to be able to do small patches of clearing, then I would do a band around the shoreline. If you clear from the edge to a water depth of 3', then any of the sunlight that does penetrate your ice should be falling on your maximum density of photosynthesizing plants.

Good luck on keeping your fish happy during this stretch of stressful conditions.

RAH - I think you are very correct - ".... that every situation is different". Probably very different
In my experienced opinion
1. The deeper the pond the larger the DO amount of consumable oxygen that will be present in the pond due to lower surface to volume ratio. The shaller the water the quicker the water layer above the bottom loses its DO. When the DO is below what it requires for that particular specie at that temperature to survive then they usually die. Different species of pond inhabitants have different tolerances to low DO or lack of it.

2. Water clarity often has a significant influence on how fast the DO is consumed during lack of sufficient sunlight for photosynthesis going on under the ice during snow covered ice conditions. The clearer the water the deeper sunlight can penetrate into more volume of the pond to stimulate the various forms of oxygen production by photosynthesis usually by most often by winter dwelling phytoplankton. Winter dwelling phytoplankton in relatively clear water can often be as many as 150,000 cells per ounce of water.

3. Most all ponds have a high amount of dead decomposing suspended detritus that creates turbidity in the water column. Thus the clearer the water has less dead suspended detritus that is present to be consuming DO. Suspended detritus enveloped by bacteria is constantly consuming DO. Amount of DO consumption is dependent on water temperature. The lower the water temperature the slower and less DO that is consumed. Thus suspended detritus and dead dying phytoplankton together due to lack of sunlight can consume measurable amounts of DO in the water column above the bottom even during winter conditions.

3. The amount of dead organic biomass in the pond has a big influence on the rate of DO consumption due to bacterial decomposition. Bacterial decomposition in the pond is by far the greatest DO consumer in the pond. Without sunlight all the photosynthetic activity ceases and then all the plant life as it dies, it decomposes and adds to the DO consumption on the bottom. The accumulated dead organic biomass on the pond bottom is the biggest consumer of pond DO, thus the loss of DO starts mostly on the bottom and advances upward. When DO is exhausted on the bottom anaerobic bacteria begin producing hydrogen sulfide (H2S). H2S is toxic to fish and almost all invertebrates.

4. Ice Conditions. Various winter conditions affect the clarity of ice and how far sunlight will penetrate through the ice for producing DO via photosynthesis. Many times during the top surface freezing conditions snow accumulates and with any melting snow and refreezing this creates a top cloudy layer. The thickness of this layer varies from ¼” to several inches thickness of cloudy milky ice. Obviously this top cloudy ice layer inhibits sunlight penetration.
Here are some examples of light transmission through ice for sufficient photosynthesis of algae and plants (Mgmt of Lakes and Ponds G.W. Bennet 2nd edition).
Some photosynthesis can occur when 10-12% of the light on the ice reaches the water below.
7.5” of clear ice permits 85% of the light to pass through
1” of snow over 3” of clear ice stops all but 10-17% of the light
5” of snow over 3” thick of clear ice allows only 2.5% light penetration.
15” of clear ice with a cloudy toping permits 11.5% of the light to pass through

Water under ice needs penetration of 10-12% of the light for some dissolved oxygen to occur from the plants. In one reference I found, if one can diligently keep about 1.1% of the pond area as snow removed from an ice covered pond it ‘should’ allow enough sunlight penetration for plant life to increase the oxygen concentration enough under the ice for fish to survive. One acre of water is 43560 sqft. And 1.1% is at least 400 to 480 sqft such as 20 ft x 25ft.

Note - Some have suggested if one can create 10% of the pond as ice free with shallow water aeration, this will allow DO by diffusion and photosynthesis to be high enough for fish survival. In one acre, this is a shoreline open water area of about a 70ft circle as ~3800 sqft. IMO more research needs to be done on this entire topic. I think the big variable in all this is - how fast does the pond lose its DO?
Ponds are highly variable for this DO loss topic as noted in the first sentence of this post and by RAH. Literature showed in one ice/snow covered pond the DO decreased from 12.3 on Feb 12 to 2.4 on Feb 14 about 5ppm per day whereas on another pond with snow cleared ice the DO increased from 1.8 ppm of Feb 5 to 8.0ppm on Feb 8 as 2.7ppm increase per day.

Note - I try to make sure that some of that snow is removed from the shallow areas of the pond where algae & some plant-life are most likely to occur and create DO when those shallow are most likely to receive sufficient sunlight for photosynthesis.

Bill - Thank you very much (once again) for taking the time to share your expert knowledge!!! My ice is about 4.5" thick and very clear, as is the water. We have been very very dry, so the pond is down over a foot and has not run through the overflow in over 4 months. We are very cold (down to -4 this morning with a predicted high of 6 F). We have about 8" of fluffy snow on the ice. I will let the neighbor (who asked to clear some patches) what you said. He fishes the ponds more than anyone else (harvests what I ask him to and releases the rest). This is exactly the type of info I was hoping for! Thank you!!! I appreciate input from Rod and Jim as well. Stay warm.

Hey everyone, this appears to be an understudied topic on Pond Boss, yet we seem to have questions on this topic every winter.

Any chance the experts (and non-experts with their own observations) can add to this thread and perhaps create a good source to be placed into the archives?

Crazy FishinRod idea to follow:

Adding salt to your fish pond can offer several potential benefits:

Reduced Osmotic Stress: As explained earlier, it eases the burden on fish osmoregulation.

Parasite Control: Salt can act as a natural treatment for certain parasites, like Ichthyophthirius multifiliis (Ich or white spot disease).

Nitrite Toxicity Reduction: Salt helps fish absorb chloride ions, which compete with nitrite for absorption into the bloodstream. Nitrite is toxic to fish, especially at higher levels.

Slime Coat Enhancement: Salt can stimulate the production of the fish’s protective slime coat, acting as a barrier against infections and injuries.
Improved Recovery from Injuries: Salt can help fish heal faster from wounds and fin rot.

Article about adding salt to a pond.

Since adding salt to a pond has lots of potential benefits, is there any chance we could use that as a time/cost effective solution for snow removal? (For pond owners that lack aeration.) I am contemplating treating some small patches to get the ice to melt and the snow to fall through. For calm, cold days the replacement ice should be relatively clear and allow some sunlight penetration.

Note - actual "rock salt" is a geologic deposit formed from evaporite basins. Even if 99% of the deposit is true NaCl, there can be all kinds of strange impurities that make up the last 1%. Several of these impurities could be harmful to fish, so any salt introduced to the pond would need to be essentially pure sodium chloride. Examples would be: pond salt or aquarium salt, or kosher salt with no iodine.

I was out shoveling today to rearrange some snow to create some snow free areas on the pond. Ice under the snow had primarily a clear top; very little cloudy ice developed this winter on my pond. Clear top ice is unusual for my winter iced pond conditions. Thus the sunlight can penetrate easily through the clear ice and easily stimulate DO production deep in the water by the phytoplankton: thus I did not clear the snow from shallow areas.

In the next few days I will collect a winter pond water sample and analyze it for phytoplankton. I will report back here the results to give readers an idea of what the phytoplankton is doing in my pond with 7 inches of snow cover on the ice. Stay tuned to this Pond Boss thread.

FishinRod or Others - Do you have any suggestions of what this thread should be titled?

Personally I don't mind non-grammatical titles that include keywords that would allow the most people to find the post.

For example: Snow removal over ice, oxygen, winter fish kill

I am sure the experts can come up with better thread titles. I just want to see people receiving maximum help for solving their problems - I hate reading the PB posts about people's fish kills.

Be careful out there, I was removing some snow this weekend and fell straight through the ice, It was a little chilly LOL

Excellent observation!

That is one of the reasons I was looking for some "non-shoveling" alternatives for pond owners.

Falling in could lead to a different kind of "Winter Kill".

This is a timely thread. I hosted an ice skating/bonfire/dog sledding event last weekend and cleared the pond of snow down to essentially glare ice (cloudy, not clear this year). Although my motivation to do this was for ice skating, it wasn't lost on me that the extra sunlight should give the DO a boost. I use a 40hp tractor with a front mounted snowblower, then drop the back blade to skim off the remainder.

In retrospect, I suppose I could have taken a sample and analyzed it for DO before and after. Unfortunately, the big snow storm that hit the Right Coast laid down another 15" of snow within 48 hours of clearing it so it's dark down there again. After reading this thread, I'll get back out there on the tractor this weekend to clear a path around the shore for skating, but I doubt I'll clear the whole pond again this year. A 12' wide path around the shore edge will hopefully be adequate to keep some O2 production during these cold months. If I remember to, I'll auger a hole to get a sample to test my DO currently.

For what it's worth, I added 750 pounds of ag salt to the pond about a month ago. I didn't do it quite as suggested by Rod, although that thought went through my mind. The pond already was pretty locked in ice for the season, but there is an inflow and outflow that are running. I've never tested the volume, but I suspect it is 25-50 GPM. It flows quickly enough that it didn't freeze even in our -10F temps. Anyways, I poured the ag salt in a small pool area at the inflow and allowed the current to dissolve it. I checked a week later and it was all gone.

My motivation to do so was a water test I had done by Texas A&M that showed my salinity was 0.031 ppt (optimal range 0.5-3ppt). They suggested "150-200 lbs of non-iodized stock salt per acre foot of water to get them into the optimal range for fish". That would be about 3,000 lbs of salt total. I bought all that the ag store had, figuring something was better than nothing. I'll send off another sample, however I wonder if it will all just wash out eventually given that I have a constant flow of water going through. I suppose the results of the next sample should help answer that.

Today, I was out at the pond and made an odd observation. The snow on the ice was gone in several spots/areas (99% still snow covered) and ther were some holes with unfrozen water away from the pond edges. A very experienced traper said the holes were not made by beaver or muskrats. Some of the holes were away from the edge over deep water where I am pretty sure there are no springs. Is it possible that the pond water itself was warm enough to melt the ice under the snow in these areas? The water has been well below full pool for many months and no surface water has entered in that time. Could the very cold weather have chilled the surface of the pond to form the ice (over 4" of ice where we cleared snow off to let light in) and then the snow blocked the current cold from reaching the ice so the warmer water below melted the ice from beneath? Could there have been a turn-over in the middle of winter? Very strange...

RAH - Here is what I think caused some holes in the ice cover with unfrozen water away from the pond edges.
My pond also had 7"-8" of snow cover on mainly 4" of ice. When I went out to collect my water sample by drilling a 6" hole in the ice, the weight of all the surrounding snow on the ice caused a lot of weight on top of the ice. All this snow on only 4" of ice put downward pressure on the iced snow area around the newly cut hole and water started noticably upwelling through the hole onto the ice until the down pressure was not strong enough to force anymore water onto the ice. After a short time while collecting the water sample, I was standing and slipping in at least 3/4" of water with water still upwelling out of the hole. The next morning I estimate at least a 50ft diameter of underlying snow of about 1" thick was water logged and then later refroze in the 0F-5F nightly temps. The next day there was still some unaffected clean snow topping the frozen snow layer below. I have seen this type of thing years previously. However in those years the nightly temps were not cold enough and the next day a slushy layer of wet snow remained under a thin layer of frozen ice.

With enough snow weight on 4" or less of ice this down pressure from snow weight I think will evenutally cause water to start seeping up through a crack or thin spot in the ice. As the water finds its way to the top of the ice, the moving water gradually melts some ice and enlarges the ice hole to allow more water to upwell through the ice hole or widen the crack. This keeps occuring until the down pressure of the weight of the snow equalizes to the strength of the ice thickness. When a pond freezes, I find that the increasing thickness of ice surface layer is not perfectly level and some pond iced areas are a little higher than other areas probably due to the expansion of the ice will heave or force some areas of the pond surface upward.

(see update at end): My neighbor used a hatchet to check ice thickness in a couple places on each of our 4 ponds when he was clearing snow. Water actually did slowly flood over the ice about 3/4" on another pond, but was frozen over the next morning such that the hole was blocked. These holes were larger than the water-filled holes visible on the pond I was discussing earlier and there was still some snow around these holes. Not saying that the heavy snow was not involved, but it still seems like something else is going on. I'll check these holes again this morning. Have not settled on alien-abduction of fish yet:) Update: Bill seems correct as usual. A morning inspection revealed the holes frozen over and larger areas that appear to have frozen slush/ice on top. I also heard the ice groan a couple times. That still does not mean the truth is not out there:)

NW Ohio pond report under winter ice and snow cover as of Jan 26 2026.
In mid-December 2025 pond had 3” of ice then it all melted and open water developed until Jan 01 26 when it refroze with subzero temps and 2-3 inches of snow cover. On Jan 25 the pond received 8” of snow.
Water sample was collected on January 26 from 14” deep over deep water ~14ft.

A standard phytoplankton analysis for the winter water condition of my pond revealed 147,946 algal cells per milliliter that equates to 4,379,201 cells per ounce of water!. All the algae were composed of very tiny cells composing 9 species and as a group that are called nanoplankton (2-20 um). No large planktonic algae forms larger than 20um were observed. Open water season algal densities almost always have some larger types of algae present in the samples.

Some other winter phytoplankton in a few select local municipal reservoirs are currently ranging in total densities of 2,000 to 80,000 cells per milliliter.

Suspended detritus density in the analyzed sample was 536,617 particles per milliliter as 15,883,863/ounce of water. Detritus is dead, decaying particulate organic material and ‘dirt’. Together the phytoplankton and detritus created a water clarity of around 3 ft. Water clarity was estimated by seeing a video camera lowered into the water and actual clarity not measured. Usually in my algal analyses, the suspended detritus is 5 to 20 times more abundant compared to the phytoplankton density, however as usual it always depends on the condition of the water body.

On one hand it is good there were lots of phytoplankton in my pond during winter. This is probably due to carryover from the Summer – Fall nutrient conditions where the water clarity ranged from 2.5 to 3ft due to the ample recycling of nutrients from the numerous introduced tilapia who were consuming available foods. On the other hand abundant phytoplankton can be bad during winter snow covered ice conditions because lack of sunlight into the pond means this could cause high numbers of dying & dead algae that would consume dissolved oxygen due to bacterial decomposition.

Advanced reading
The study of winter phytoplankton under ice cover has been a relatively unstudied science. Interest in the condition of that type of habitat is increasing. A few years ago I participated in the algal analyses and was co-author of a research study called the Winter Grab that reported on the phytoplankton under winter iced conditions of all five of the Laurentian Great Lakes that compose the largest freshwater ecosystem in the world.
https://doi.org/10.1002/lol2.10447

Ice formation is typically a complex DYNAMIC phenomenon. Pond ice is not a static creation, but rather goes through many freezes and partial thaws during the period where net ice is increasing.

In the simplest version, ice forms at the edges of the pond, and the center freezes last. This mostly due to the to the densest water at 39F sinking down the pond slope and going to the deep spots with the remaining water at the edges cooling down to 32F and freezing.

However, at a smaller scale you can frequently observe open water right at the very edge of the pond while there is a band of ice growing towards the middle. This is for two reasons.

First, the soil of your pond banks below the frost line is MUCH warmer than the water in your pond. The soil at depth will be approximately the average annual temperature of your geographic location. There will then be a decreasing temperature gradient from that point to the soil at the air interface. This small bit of geothermal heat does help warm the water at the very edge of your pond.

Secondly, even on a very cold day, but with bright sunshine, the dark materials at the edge of the pond can absorb a lot of incoming solar radiation. It can be 15F for the air temperature, yet the soil at noon may have heated up to 40F on a calm day.

Finally, right at the edges where the water is only a 1/4" deep, the maximum ice thickness is also only a 1/4". If the water level in your pond goes down a 1/4" or more during a month-long freeze, then the edge ice can melt on a warm day and run back into the pond in patches. Other patches may also melt, but the deeper ice blocks the meltwater from leaving the area, so that area subsequently re-freezes.

If you observe your ice holes and consider them in the light of a complex, dynamic environment do all of those mechanisms make possible the actual structures you are observing?

(If not, then please put out same game cameras. I am sure we would all love to see the pics of aliens you post to the forum. )

I was seeing the same thing as Bill Cody and some of the above, any place where there was a protrusion thru the ice, that wound up letting water up thru the ice wound up in a huge, 50' plus diameter of water logged snow around the perimeter of whatever protrusion created the hole, the weird part was, even after some really cold weather for several nights, the slush only crusted over and there was still a wet, soft layer between the original ice and the surface which had obviously crusted over but to me should have been frozen solid after several single digit days.

As a beer league hockey player, I am always interested in trying to get my pond ice in a good state for skating. This year has been troublesome! The first part of winter, we were low pool, but the ice surface was in decent shape, except for a very slow rise in water. This opened a gap in the ice around the perimeter of open water, while the center floated with nice 3-4” ice. Of course nobody wanted to play on that as the pucks would all be lost quickly. Plush it was sketchy near the edges.

Then we had a thaw, and the water level rose to full pool. It lifted my dock with it, and left that nice sheet of ice stranded 4’ out in the center. The ice melted enough that the 500lbs of concrete blocks pushed the dock back down at least.

Then it refroze to the edges, and was well ripened until we had a wind storm. That popped holes in the ice, and pumped water in and out of the holes with the wind. 5” of ice compromised by that wind storm! However, that resurfaced the ice into perfection when it finally refroze. Then we had 4” of fluffy snow, and the ice held up well. Nobody was able to come help shovel off a rink, but that appeared to be the one good day.

Then we got 18” of snow, and the weight pushed the ice downwards, and a lot of water flowed into the snow. The thin layer of snow left on top is excellent insulation, so it took a long time to refreeze. Now it is like frozen layer cake. Useless for skating, yet very thick, especially in the center. Last time I checked last weekend I stopped drilling a hole at 6” where previously there was no ice. It hasn’t gotten above 12 degrees since then.

It is the longest stretch of below 20F weather here since 1979 when Lake Ontario froze from shore to shore.

If you are very good in 2026, maybe Santa will bring you a Zamboni for Christmas!

Drilled a couple holes through the 11" of ice today and with the 7"-8" of snow on top the water still wanted to upwell and onto the ice. I has been a long time since the pond has had 11" of ice.

I’ve never seen 11” of ice.

David - Travel northeast to Ohio and I will let you drill through the 11" of ice and even catch a dandy world famous yellow perch for dinner. Yours truly, BCody

To me, auguring through 11" inches of ice for a world famous yellow perch dinner seems like a very small price to pay!