Pond Boss Forums AERATION Systems questions IceFishing

Message was enhanced by Cody Oct 31.
ewest asks "how long would it take to go from enough DO to allow catching fish near the bottom to winter kill assuming snow > 4" and no removal." It depends on the pond depth. But if pond was 8-10 ft deep my best guess would be about 5-10 more days. I think in many cases the DO loss gradually works its way up from the bottom toward the top. The fish gradually move higher into the water column as DO is lost from the bottom toward the surface. In winter under ice cover the water is typically pretty clear. The more cloudy the water, usually the more rapid the DO loss from bottom to top will occur due to additional biochemical oxygen demand from more cloudy water in the entire water column. Thus the clarity of the water will have a big affect on how long the DO will last until the DO in water near the surface (upper 2-3ft) finally drops below 1-3 ppm(mg/L) - in many cases the killing concentration at cold temps of 39F (depending on species of fish).

ewest's 2nd question was ""How much would drilling a few holes (3 to 4) ice fishing sized in a 1/2 acre pond help with DO concerns.""

Diffusion of oxygen from the air into water is so very, very slow that the amount of DO that could diffuse into a real small surface area of water of a 6" diameter ice hole (28sqin)would be IMO an almost unmeasurable amount especially if measuring it a foot or two away from the hole under the ice.

In many cases an ice skim usually reforms relatively quickly in the open ice hole which stops any additional oxygen transfer. Any small amount of oxygen that might transfer into the water has to gradually work its way down through the 6" diameter column of water of the ice hole thickness (4"-18") and without currents this could take days to get a small amount of DO into water directly below the ice layer even 2 ft deep.

One of my limnology books says that it will take 6.7 days for the DO to increase 1 ppm at a depth of just one inch deep when relying solely on diffusion of oxygen from the air through the surface tension of the water into quiet unagitated water. Thus if the hole in ice 6" thick could be kept open, it would take 40 days for an increase of 1ppm DO to reach the small area of water under 6" of ice at the hole. I think the biggest benefit of any measurable increased DO from boring a hole through the ice is that it allows light to readily reach a small area of water near the hole. This stimulates phytoplankton to produce oxygen in the area surrounding the ice hole.

I continually keep preaching that removing snow for phytoplankton photosynthesis that is suspended throughout the water column or any green rooted plant or filamentous algae which receives sunlight, results in production of dissolved oxygen where ever the plants receive light at the 1% incident surface level. This results in much more oxygenation of the water column of the pond/lake compared to a small 4"-8" diameter briefly open water hole in the ice. And since water under ice cover is usually clear and most of the ice thickness is clear as glass any light making it into the water penetrates relatively deeply into the pond. Light into very clear water during winter often penetrates to the bottom if depths are less than 20 ft. In these cases, DO levels can rise rapidly if no snow cover stops light penetration through ice. The top layer of ice is often cloudy (frozen slush) which reduces the amount of light that penetrates into the water thus more snow needs to be removed in these cases where cloudy top ice is present.