Pond Boss Forums AERATION Should I aerate? Winter aeration

The main thing we worry about wrt Winter aeration is having enough oxygen for the fish under the ice. On the plus side, the fishes' BOD is lower in cold water and cold water will hold more oxygen to start with.

Bill Cody has posted some good figures; IIRC the Winter phytoplankton in a pond should be able to produce enough O2 for the fish if a minimum of 10% or so of the ice surface is kept free of snow to let sunlight through the ice. So if aeration were the only way to keep part of the pond snow-free, you would definitely want to aerate enough to keep a small part of the pond clear. Note that "according to Cody" (which is plenty good enough for me) it would be OK if the ice froze over the cleared space (if the resulting ice stayed clear of snow).

Clear "black" ice will transmit more light into the pond than slushy/dirty/refrozen ice. The lighter the ice appears to us, the more light is reflecting off of the ice and the less it is being transmitted into the pond.

(Bil, if I'm getting any of this wrong, please correct me.)

The secondary thing we worry about with Winter aeration is possibly stressing the fish by supercooling the pond water. In an iced-over pond, the warmest water will be on the bottom and will be about 39 deg F/4 deg C (water is it's densest at this temperature, and in the absence of mixing from wind or aeration, the densest water sinks to the bottom). If we aerate, for too long and in deep water, we can send this "warm" 39 deg F water up to the surface (where it cools) and eliminate the (relatively) warm refuge fish have at the bottom of the pond. So if you have to aerate in the Winter to maintain sufficient O2, it is better to do so sparingly, or in shallow water, or both.

I personally suspect the severity of the effects of supercooling are dependant on what species of fish are in the pond - I think warm-water loving species tending to come from the South (like RES) will be more bothered by supercooling than cool-water loving species from the North (like Walleye or Northern Pike). But even cool water fish may be better off with no stress from supercooling.