Pumping under the ice

[Lisak1]

Very cool! What kind of camera are you using? The pics are so clear!

 

[DeepWater]

It's a TrendNET 4 MP security cam, PoE networked and mounted under the eve of the porch. Motion areas setup near the bog, waterfall, and bird feeder. When motion detected, it FTPs a series of 5 images. It works great during nice weather, but a foggy, snowy, or rainy night will send 15,000 images...

 

[Waterbug]

I know it's been popular online to pump water during the winter for various reasons but I rarely see anyone mentioning the risk. So I will. An ice covered pond will have water that is about 32F just under the ice and about 39F near the pond bottom. Water is most dense at about 39F so it sinks while 32F will rise. The fish will generally hang out on the bottom to stay "warm". The ice helps to insulate the water from the normally much colder air and keeps the water nice and calm so the water can stratify. Pumping water stops the stratification by mixing. Now the temp is likely the same throughout the pond and close to 32F because heat moves slower into the water than temp is reduced by ice contact.

Fish can survive in very cold water for periods of time. But as the length of time increases and fish no long have access to the warmer 39F water the risk to fish increases. Same with humans.

 

[Meyer Jordan]

The minimum temperature of the water at the bottom of a pond is strongly influenced by the depth of the pond.
In shallow ponds stratification does not develop.

 

[addy1]

oh no ,so u cant see if they r ok?

I really don't worry about them when the pond is ice covered. The fish just hang out, barely moving.

Once it melts, they come out.

Right now ice covered, a week ago the pond was 56F right now it is 38F(bottom temp) with a covering of ice. I saw the herd last week when it was 70F (air temp, pond around 56F)

 

[DeepWater]

This is just how I started the thread, wondering if drawing the pump's water from 2' or 5' deep would make any difference in maintaining warmer water near the bottom. I went with the early answer that with a max of 5.5' deep, the stratification would be negligible if it existed at all. I kept both valves open and drew water from 2' and 5'. I'd guess though, that with the pump off and a solid ice formation, it would be a few degrees warmer down there.

I have no koi or goldfish yet. I hope to add a few same sex goldies this spring after the water gets up to 70 or so. The pond has several dozen rosy red minnows. When the pond thawed over the last few weeks, those rosy reds were brightly colored and active. No evidence of any dead ones.

I enjoy the running water in the winter. The waterfall and stream section are visible from the house, and the birds still drink from and bath in even the smallest part of moving open water. Our feathered friends make it all worth it!

 

[Lisak1]

In shallow ponds stratification does not develop

How shallow is shallow?

 

[Meyer Jordan]

How shallow is shallow?

"The depth of the thermocline below the surface may fluctuate from 2 or 3 m in shallow
lakes to 10 m or more in deeper lakes, depending on weather conditions."
Pond Aquaculture Water Quality Management Claude E. Boyd, C.S. Tucker

"In artificial ponds where the depth is usually of 1 – 2 metres there will be only a minor
difference between the surface and bottom water".
FAO United Nations

 

[Lisak1]

Thanks!

 

[Waterbug]

Thermocline and stratification are indeed a deep water phenomenon. They're also unrelated to water temp and ice in shallow ponds because, well, they're shallow. Here density, conduction and convection would be the relevant phenomenons to consider. Ice acts an insulator slowing the transfer of heat between the cold air and the warm water and the even warmer ground. The ice is 32F and the ground is say 40F, maybe higher. Heat transfers from the ground to the water, and that heat transfers (conducts) up. Doesn't matter how deep the water. And 39F water being heavier means convection works opposite to what we might normally think which slows conduction even more. These relevant phenomenons are responsible for why fish can survive under ice and why most in ground ponds don't freeze solid in most conditions.

Science aside...would you want to be closer to the 32F ice or the 40F ground? Yeah, I know, neither.