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November 2012

03-26-13 Winter


The Incredible Transformation

Winter is coming and none-too-soon after the hottest summer on record in Wisconsin.  Winter is one of my favorite times; I am particularly fond of watching ice form on the lake across from my house.  When the water temperature reaches 32°F, it just waits for a windless night so it can accumulate a thin layer of ice over the entire three mile surface.  I will go to bed watching waves and wake up to a sheet of glass.  This is an incredible transformation and a good sign that we will be going ice fishing soon, which is the best way to fish, in my northern opinion.

During the winter your fish, plants, and aquatic life slows down.  The plants are still there and you may be able to see them under the ice.  I encourage many pond owners to use the slow time to do testing.  Running tests while the temperatures are cool will give you a baseline of results that you can compare from year to year.

We suggest you test for:


<0.1 ppm is considered non-polluted

The lethal levels for fish vary 0.05 to 2.0 ppm.  Fish, waterfowl, and fertilizer are the largest contributors



The top layer of the lake may have low levels due to algae uptake.  Bottom layer will be higher due to decay.  Algae use NO3 as nitrogen source for growth.  Less than 0.5 ppm preferred.



<0.01 ppm = good

<0.02 ppm = generally avoids overgrowth

>0.025 ppm = plant growth is stimulated, expect problems with weed and algae growth



0-60 ppm = soft

120-180 ppm = hard

Desirable range is 50-150 ppm

Minimum acceptable 10 ppm

The harder the water the more difficulty algaecides have.

However, bag bass like hard water.



Optimal is 50-150 ppm

Acceptable 20-400 ppm

Measure your water’s ability to withstand pH swings often caused by algae.



Desirable range is <0.1 ppm

Pithophera is a filamentous green algae caused by iron in the water



Surface layer commonly 7-8.5

Bottom layer commonly 6-7.5


There are many other things you can test for but these are the basics.  It’s nice to see how they change from year to year and in response to the management of the pond.


In addition, if you have any reason to be concerned with dissolved oxygen you can get a professional applicator to run a dissolved oxygen test.  Although dissolved oxygen saturation improves in cold water, if you have a shallow pond and get a couple feet of ice on it, oxygen can deplete.  Some pond owners aerate in the winter to keep a hole in the ice, but, be careful how you do this for safety reasons.  They also aerate to keep the water from becoming too cold.


Your Pond Stratifies in the Winter

Cold water rises to the top and at 32°F it forms ice.  Directly below the ice the temperature is 33°F and on the bottom of the pond sits warmer water.  The temperature will vary depending on the depth of your pond and the temperature at the surface.  But, it’s common to find water pushing 40°F at the bottom of the northern ponds.


Cold Water and Algae

Just because your water temperature is cold does not mean the algae will not grow.  If algae can grow under the ice in Antarctica, it can grow in your place.  These are green and possibly some blue-green algae; they may be eaten by fish or other organisms in the pond but their presence should not be a complete shock.  Algae are not all bad to have in your pond when they are manageable.  The higher your ammonia and phosphorous the more likely algae will grow.  If you find out your pond is loaded with nutrients and you see algae and plants starting to grow in February, when temperatures are typically coldest, then you need to do your homework to make sure your pond is a pleasure for next summer.


Bacterial Growth in Cold Water

For every 5°F drop in temperature, the growth rate of your naturally occurring bacteria will be cut in half.  This is important because bacteria consume phosphate, nitrogen, and many other nutrients.  If you have a pond that has an abundance of fish or ducks, then you may want consider adding a cold temperature bacteria culture.  Special cold temperature bacteria help to control nutrient loading in the winter.


For our company, winter is a chance to study many of the unique algae and aquatic plants that come into our lab over the summer.  We get samples from readers of Pond Boss and professional applicators and we work on growing them.  That’s right…we grow them to study.  That is because we first need to learn how to grow them before we can understand how to deal with them.

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