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Keep Fish Alive This Winter - De-Icers

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September/October 2012

Joe Holz

A major fear of any fish pond owner here in the north is winterkill. Simply using a De-Icer, Diffuser, or Water Circulator will create an opening and maintain an ice-free area to allow for proper oxygen levels and limit the chances of a winterkill situation this winter.

Winterkill is caused by a lack of oxygen under the ice. Large amounts of snow and ice encase ponds and prevent oxygen from being added to the water by effectively limiting light penetration and oxygen transfer at the air/water interface. Most plants will die off during this time because sunlight is severely limited and blocked from the snow/ice layer. This is a double whammy. First, you have no added oxygen from photosynthesis since the plants die. Second, the increasing load of organic matter creates higher Biological/ Oxygen Demand with bacteria consuming both oxygen and the organics. Fish will eventually run out of oxygen and may die.

A simple way to prevent all this trouble in large ponds is to maintain an open water area. Cold water has the ability to hold large amounts of oxygen vs. warm water. Therefore, simply exposing water to the atmosphere will allow sufficient amounts of oxygen to be absorbed into the water and maintain healthy DO (Dissolved Oxygen) levels for fish and other living organisms.

Some studies suggest as little as 1-2% of the surface area need to be ice free to prevent winterkill situations. This can easily be achieved using a De-Icer, Diffuser, or Water Circulator. These products work by pushing/moving warmer bottom water that is heated by the earth up to the surface to remove and prevent ice formation. All of these products produce large volumes of water flow, but do not splash the water at the surface. In fact, splashing will expose water to the air too much and can cause super cooling which will drop the water temperatures to dangerous levels for the fish and, in shallow ponds, can virtually create a giant slush pit.

De-Icers and Water Circulators can be mounted on horizontal floats at the surface, rigid mounted to a dock, piling, or wall with a Dock Mount, or hung below boats and docks with ropes. Diffusers, such as Robust-Aire, use a compressor mounted on shore to pump air to the bottom of the pond, which then turns large volumes of water. With any of these choices, it is best to position at or near the deeper portions of the ponds. Diffusers are typically best in 8´+ depths. The Horizontal Floats often are not the best choice for extreme northern temperatures as they do not have as much access to the warmer, deeper water, but work very well in more moderate temperature areas.

In small, shallow backyard ponds and water gardens, these types of devices are often too large and will not work effectively in these applications. It is best to use small pond heaters for de-icing these ponds as the larger devices will move too much water volume and create a super-cooling situation.

This year put your customers’ minds at ease by installing a de-icing product and protect their fish and pond investment from winter’s worse. Not only will it bring you business in a slower time of year, but it will save you and your customers the head and heart aches from a pond full of dead fish.

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