Question about winter temps


Jkm

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quote from a 2017 thread:
“MitchM: FWIW, if you have any ice cover plus water circulation, your pond will have zero difference in temperature between the top and bottom. The entire water body will be about 32.5F. I have sensors at the 2 foot and 5 foot level and have seen the difference even a little circulation can make.”

I’m in north Idaho, zone 6, with a brand new pond which is not established yet. This summer I inadvertently killed all my young goldfish with overdoses of AlgaeFix, which seemed like a good idea at the time but was not. So the Pond of Death is devoid of fish for this first experimental winter, but the plumbing is all in place and functional. The pond is approx. 10,000 gallons (thank you, MitchM, for your calculations), 5’ deep at the drain, separately valved waterfall, skimmer, drain, and subsurface outflow 18” down and aimed at the surface.

Air temps are currently down to mid-twenties at night, and will get a lot colder. Water in unheated horse water buckets freezes 1/4” overnight. The pond drain is turned off, but the waterfall, subsurface flow and skimmer are all running. No ice on the pond. I check the temps around the surface and at the drain several times a day out of curiosity. (I have a sinking fly-fishing thermometer lying near the drain that’s tied to the bank with fishing line so I can pull it up quickly).

The temps currently around the surface are 37F, and the temp at the drain this morning was 32F.

My question is: Given adequate open surface for gas exchange, can goldfish survive 32F at the bottom?
 
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Jkm

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Thank you - you are immensely helpful.

Just read the thread. Wow, am I relieved!
 
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quote from a 2017 thread:
“MitchM: FWIW, if you have any ice cover plus water circulation, your pond will have zero difference in temperature between the top and bottom. The entire water body will be about 32.5F. I have sensors at the 2 foot and 5 foot level and have seen the difference even a little circulation can make.”

I’m in north Idaho, zone 6, with a brand new pond which is not established yet. This summer I inadvertently killed all my young goldfish with overdoses of AlgaeFix, which seemed like a good idea at the time but was not. So the Pond of Death is devoid of fish for this first experimental winter, but the plumbing is all in place and functional. The pond is approx. 10,000 gallons (thank you, MitchM, for your calculations), 5’ deep at the drain, separately valved waterfall, skimmer, drain, and subsurface outflow 18” down and aimed at the surface.

Air temps are currently down to mid-twenties at night, and will get a lot colder. Water in unheated horse water buckets freezes 1/4” overnight. The pond drain is turned off, but the waterfall, subsurface flow and skimmer are all running. No ice on the pond. I check the temps around the surface and at the drain several times a day out of curiosity. (I have a sinking fly-fishing thermometer lying near the drain that’s tied to the bank with fishing line so I can pull it up quickly).

The temps currently around the surface are 37F, and the temp at the drain this morning was 32F.

My question is: Given adequate open surface for gas exchange, can goldfish survive 32F at the bottom?
I am in Md. zone 7 and my 13 large koi stay on the bottom of my 2900 gal pond ( 36" deep ) all winter with no ill effects at all. I cover the pond with clear reinforced poly on a frame and the water hardly ever freezes. I shut down my filter and only run 2 aerators 1' down and a de-icer if needed. I would be careful running the filter with a water fall all winter as I did . The cold temps froze the water fall and the water was leaving the pond from the rear. Fortunately I caught it early with no major issues. Good luck
 
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It's quite interesting. My pond is 36-38" deep. at the present time I have 12" plus of ice on the surface of the water and the ambient temps can be hovering in the single numbers at night and teens during the day. Science tells us that at the interface of the water/ice the temp is 32 deg. so I have approx 24" of water. Dropping a thermometer to the bottom I learned the temps there were 36-37 degrees. I was surprised to discover it was this high.
I have a 9" low wattage heater to keep a hole open for gas expulsion, but that is the only area that is open to ambient temps. Nothing is running or circulating the water.
The most amazing thing I've discovered is each spring there are more fish then there were when I closed the pond in the fall. Of course they're juveniles, but it proves they'll hatch in cold water or warm.
 

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