Pond & Lake Q & A
Recently, someone asked me a fantastic question regarding winter aeration and if it can “super-cool” your pond in the winter, possibly causing harm to your fish. I had one of our expert Fisheries Biologists, Justin McLeod, answer this question. Below are some easy solutions that he suggests to ensure a fish-safe winter for those of you in the colder climates. – Jason Blake, The Pond Guy®
Winter aeration (bubblers) can be very important in areas where ponds can freeze over. Along the Northern US border and into Canada, mid-winter temperatures dip well below freezing for prolonged amounts of time. This can put your fish into jeopardy if the pond freezes completely over. To answer your question regarding “Super-Cooling your pond, extremely cold surface temperatures cause ponds to stratify in the opposite way of the summer. Because water is most dense at 39 degrees Fahrenheit, the water beneath the winter thermocline stays around that 39 degree mark, while the water above the thermocline drops down near the 32 degree mark. This is a small difference, but it could mean life or death to a fish.
A “super-cooled” condition is created generally when surface aeration (fountains, High Volume Surface aerators, or really anything pump or pushing water into the atmosphere) is used during winter months. “Super-Cooling” happens when the colder water on the top is circulated to the bottom, leaving no warmer water refuge for the fish. Although it is uncommon to see “Super-Cooling” with sub-surface aeration (bottom bubblers), there have been instances when it has happened. With that said, I would never let this stop me from operating my aerator in the winter – my fish are just too important to me!
Here are some tips to make sure you get the most out of your aeration system and possibly avoid the chance of “Super-Cooling”:
- 1. If you have multiple diffuser plates, it is ok to run only 50% of your diffusers. Even though the mixing power of your system is decreased, it will still add oxygen to the pond and allow gases to escape out through the hole it creates in the ice. Note: You only need 10% of your water surface open in the winter for gas exchange.
- 2. If your pond is extremely small (1/8 acre or less), you may want to move your plate(s) out from the deepest area into a shallower spot. This will leave room for fish to winter in the deeper water.
POND TALK: What do you do to prepare your lake fish for winter?
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