Q: What is supercooling?
Aloma, Warroad, MN
A: Supercooling is uncommon, but it can occur in lakes and ponds, particularly in the northern states. Here’s what you need to know about it and how to prevent it from happening.
In the winter time water stratifies in pond and lakes without proper aeration when surface temperatures are extremely cold, creating what’s called a thermocline. A thermocline happens as warmer water about 39°F or so – sinks to the bottom, while colder water about 32°F or so – rises to the top. Very little mixing of the layers occurs, particularly in calm weather.
Supercooling could become an issue if you’re running a surface aeration system in shallow ponds with fish. The fish prefer to stay on the bottom of the pond in the warmer pockets of water during the winter. They’re in winter-hibernation mode, and all they want to do is be in a stress-free spot until spring.
As the aerator circulates the warmer water with the cooler water at the surface, the overall temperature could drop. In extreme cases when the temperatures are well below 0°F, the water temperature can actually drop below its freezing point without becoming a solid – a rare process known as supercooling.
If the water gets too cold, your fish have nowhere warm to go. Living without their warm hangout spot could compromise their oxygen supply and immune systems, making them vulnerable to parasites and diseases.
The best way to deliver oxygen to your fish is with a bottom diffused aerator, like an Airmax® Aeration System. You can keep it running without creating an inhospitable environment for your finned friends by simply moving your diffuser plates closer to the surface or turning half of them off.
If you relocate the diffuser plates to a spot that’s about half the depth of your pond or run only 50 percent of them, a pocket of warm water will remain for your fish at the bottom. You’ll continue pumping oxygen into the water and keeping a hole in the ice for gas exchange without having to worry about freezing your fish.
Pond Talk: What steps do you take to prevent over cooling or supercooling your pond?
