Starved to death?

[ba5416]

The ice came off the pond a week or so ago. Found several fish floating on
the surface and several on the bottom. Pond is about a 1000 ga, 4ft deep at
the deep end. Pond has been in place for 4 years now with no problems. I
leave the pump running 24/7/365, turn the fountain off and leave the
waterfall run to keep things open.
Did the water quality tests once I found the dead fish. Everything was OK.
I did a major cleanout of the pond last Aug by netting all the fish (about
40 from 5" down to 1/2", removing the plants, draining the water and sucking
up all the black ooze that was on the bottom. Replaced all the water, (we
are on a well), did water samples, replaced the fish, fed the fish until
water temps dropped below 55 and waited for winter. Is it possible that with
the cleaning there were not as much food for them to forage on over the
winter? I have had more fish die in the past couple of days. The three
original fish from the beginning are still there and getting active. I
netted a couple of the smaller ones that were born in the pond and do not
see any issues with the gills or scales. I did a basic autopsy on one of the
dead fish and the stomach was totally empty.

I am stumped with this one. Did they starve or is there something else going
on.

[Reel McKoi]

"ba5416" > wrote in message
...
> The ice came off the pond a week or so ago. Found several fish floating on
> the surface and several on the bottom. Pond is about a 1000 ga, 4ft deep
at
> the deep end. Pond has been in place for 4 years now with no problems. I
> leave the pump running 24/7/365, turn the fountain off and leave the
> waterfall run to keep things open.
> Did the water quality tests once I found the dead fish. Everything was
OK.

$ You didn't allow the fish to find the "warm spots" at the bottom of the
pond and rest for the winter. The current and cold probably killed them.
Just about everyone in a cold climate turns the waterfalls etc off to allow
this natural rest period - and so that the water can do it's natural
conversion (cold at the top, warmer and still at the bottom.)

> I did a major cleanout of the pond last Aug by netting all the fish (about
> 40 from 5" down to 1/2", removing the plants, draining the water and
sucking
> up all the black ooze that was on the bottom. Replaced all the water, (we
> are on a well), did water samples, replaced the fish, fed the fish until
> water temps dropped below 55 and waited for winter. Is it possible that
with
> the cleaning there were not as much food for them to forage on over the
> winter?

$ They don't eat when the water gets cold.

I have had more fish die in the past couple of days. The three
> original fish from the beginning are still there and getting active. I
> netted a couple of the smaller ones that were born in the pond and do not
> see any issues with the gills or scales. I did a basic autopsy on one of
the
> dead fish and the stomach was totally empty.
>
> I am stumped with this one. Did they starve or is there something else
going
> on.

$ You have too many fish in only 1000 gallons of water. You didn't allow
them a "rest" when the water temps dropped. Having to deal with a current
when they should be "asleep" can, does and will kill them.
--
McKoi.... the frugal ponder...
~~~ }<((((o> ~~~ }<{{{{o> ~~~ }<(((((o>

[George]

"Reel McKoi" > wrote in message
...
>
> "ba5416" > wrote in message
> ...
>> The ice came off the pond a week or so ago. Found several fish floating on
>> the surface and several on the bottom. Pond is about a 1000 ga, 4ft deep
> at
>> the deep end. Pond has been in place for 4 years now with no problems. I
>> leave the pump running 24/7/365, turn the fountain off and leave the
>> waterfall run to keep things open.
>> Did the water quality tests once I found the dead fish. Everything was
> OK.
>
> $ You didn't allow the fish to find the "warm spots" at the bottom of the
> pond and rest for the winter. The current and cold probably killed them.
> Just about everyone in a cold climate turns the waterfalls etc off to allow
> this natural rest period - and so that the water can do it's natural
> conversion (cold at the top, warmer and still at the bottom.)

I see that you flunked thermodynamics. Cold water sinks. Warm water rises.

[Elaine T]

George wrote:
> "Reel McKoi" > wrote in message
> ...
>
>>"ba5416" > wrote in message
...
>>
>>>The ice came off the pond a week or so ago. Found several fish floating on
>>>the surface and several on the bottom. Pond is about a 1000 ga, 4ft deep
>>
>>at
>>
>>>the deep end. Pond has been in place for 4 years now with no problems. I
>>>leave the pump running 24/7/365, turn the fountain off and leave the
>>>waterfall run to keep things open.
>>> Did the water quality tests once I found the dead fish. Everything was
>>
>>OK.
>>
>>$ You didn't allow the fish to find the "warm spots" at the bottom of the
>>pond and rest for the winter. The current and cold probably killed them.
>>Just about everyone in a cold climate turns the waterfalls etc off to allow
>>this natural rest period - and so that the water can do it's natural
>>conversion (cold at the top, warmer and still at the bottom.)
>
>
> I see that you flunked thermodynamics. Cold water sinks. Warm water rises.
>
>
I see you fluked chemistry. ;-) Water is at its absolute highest
density at 4 degrees C, above freezing. Because of this, interesting
thermal stratifications can occur in cold, still water.

--
__ Elaine T __
><__'> http://eethomp.com/fish.html <'__><
rec.aquaria.* FAQ http://faq.thekrib.com

[George]

"Elaine T" > wrote in message
om...
> George wrote:
>> "Reel McKoi" > wrote in message
>> ...
>>
>>>"ba5416" > wrote in message
...
>>>
>>>>The ice came off the pond a week or so ago. Found several fish floating on
>>>>the surface and several on the bottom. Pond is about a 1000 ga, 4ft deep
>>>
>>>at
>>>
>>>>the deep end. Pond has been in place for 4 years now with no problems. I
>>>>leave the pump running 24/7/365, turn the fountain off and leave the
>>>>waterfall run to keep things open.
>>>> Did the water quality tests once I found the dead fish. Everything was
>>>
>>>OK.
>>>
>>>$ You didn't allow the fish to find the "warm spots" at the bottom of the
>>>pond and rest for the winter. The current and cold probably killed them.
>>>Just about everyone in a cold climate turns the waterfalls etc off to allow
>>>this natural rest period - and so that the water can do it's natural
>>>conversion (cold at the top, warmer and still at the bottom.)
>>
>>
>> I see that you flunked thermodynamics. Cold water sinks. Warm water rises.
> I see you fluked chemistry. ;-) Water is at its absolute highest density at
> 4 degrees C, above freezing. Because of this, interesting thermal
> stratifications can occur in cold, still water.
>

I was waiting for someone to bring this issue up. It was discussed at length
last fall. In an effort to see how this affects shallow garden ponds, I
conducted a little experiment, measuring the water temperature at the surface,
and comparing it with water at the bottom (45").

Starting with autumn, let's see how the pond changed into the winter. The water
at the surface started out in October at 42°F. The first frost and cold wind
lowered the surface layer and it sank, while the warm water rose and replaced it
and was chilled in turn. This circulation process continued until all the water
reached 39.2°F, at this temperature water is at its heaviest. Normally, any
cooling beyond 39.2°F does not sink, instead forms a thin layer at the surface
because of the local geothermal gradient, which will warm any water that is
below the frost line. However, with shallow ponds, the cold water can continue
to sink (especially if the pond is not dug below the frost line), and cause the
pond to continue to cool, and if this process continues, the pond can freeze
completely to the bottom. When the weather is cold enough the surface freezes
at (32°F). Freezing at the surface helps to stop the circulation, and the warm
water will stay at and below the frost line. Interestingly, when my pond
started to freeze (it only froze slightly on the very ends because I use a
de-icer), the fish didn't stay on the bottom, but hovered just below the ground
surface (my pond is 18" aboveground, and 27" below ground, so they hovered at
about 18-20" below the water surface). In other words, they stayed about a
third of the way down in the pond. Before the ice began to form, but while the
air temperature was still dropping, the water at the bottom continued to drop
until it reached a temperature of 34-35 degrees, at which time it stabilized
Which was about the same temperature as the water just below the surface (about
4 inches). It never dropped below this temperature range. When the temperature
was just above freezing, both the surface and the bottom water stayed around
34-36 degrees. The point is that unless a garden pond is dug well below the
frost line, you are not likely to see much of the stratification you normally
would see. This is why ponds that are not dug below the frost line can and do
freeze solid during a cold winter.

[Reel McKoi]

"George" > wrote in message
news:NuK4e.6628$g65.5582@attbi_s52...
>
> "Reel McKoi" > wrote in message
> ...
> >
> > "ba5416" > wrote in message
> > ...
> >> The ice came off the pond a week or so ago. Found several fish floating
on
> >> the surface and several on the bottom. Pond is about a 1000 ga, 4ft
deep
> > at
> >> the deep end. Pond has been in place for 4 years now with no problems.
I
> >> leave the pump running 24/7/365, turn the fountain off and leave the
> >> waterfall run to keep things open.
> >> Did the water quality tests once I found the dead fish. Everything was
> > OK.
> >
> > $ You didn't allow the fish to find the "warm spots" at the bottom of
the
> > pond and rest for the winter. The current and cold probably killed
them.
> > Just about everyone in a cold climate turns the waterfalls etc off to
allow
> > this natural rest period - and so that the water can do it's natural
> > conversion (cold at the top, warmer and still at the bottom.)
>
> I see that you flunked thermodynamics. Cold water sinks. Warm water
rises.
==========================
Excuse me,.... not in the winter. That's why ICE forms on top first - and
works it's way down. My ponds stay around 40 F at the bottom when the
surface is 32 and freezing. Looks like YOU flunked thermodynamics.....
--
McKoi.... the frugal ponder...
~~~ }<((((o> ~~~ }<{{{{o> ~~~ }<(((((o>

[Reel McKoi]

"Elaine T" > wrote in message
om...
> George wrote:
> > "Reel McKoi" > wrote in message
> > ...
> >
> >>"ba5416" > wrote in message
> ...
> >>
> >>>The ice came off the pond a week or so ago. Found several fish floating
on
> >>>the surface and several on the bottom. Pond is about a 1000 ga, 4ft
deep
> >>
> >>at
> >>
> >>>the deep end. Pond has been in place for 4 years now with no problems.
I
> >>>leave the pump running 24/7/365, turn the fountain off and leave the
> >>>waterfall run to keep things open.
> >>> Did the water quality tests once I found the dead fish. Everything was
> >>
> >>OK.
> >>
> >>$ You didn't allow the fish to find the "warm spots" at the bottom of
the
> >>pond and rest for the winter. The current and cold probably killed
them.
> >>Just about everyone in a cold climate turns the waterfalls etc off to
allow
> >>this natural rest period - and so that the water can do it's natural
> >>conversion (cold at the top, warmer and still at the bottom.)
> >
> >
> > I see that you flunked thermodynamics. Cold water sinks. Warm water
rises.
> >
> >
> I see you fluked chemistry. ;-) Water is at its absolute highest
> density at 4 degrees C, above freezing. Because of this, interesting
> thermal stratifications can occur in cold, still water.
==================
Thank you Elaine. When the water goes through this conversion in the fall
the fish remain almost unmoving in the still water at the pond bottom. A
current of colder water at this time is not good for them.
--
McKoi.... the frugal ponder...
~~~ }<((((o> ~~~ }<{{{{o> ~~~ }<(((((o>

[Reel McKoi]

"George" > wrote in message
news:J5M4e.15943$Vx1.13708@attbi_s01...
> Starting with autumn, let's see how the pond changed into the winter. The
water
> at the surface started out in October at 42°F. The first frost and cold
wind
> lowered the surface layer and it sank, while the warm water rose and
replaced it
> and was chilled in turn. This circulation process continued until all the
water
> reached 39.2°F, at this temperature water is at its heaviest. Normally,
any
> cooling beyond 39.2°F does not sink, instead forms a thin layer at the
surface
> because of the local geothermal gradient, ...........
============================
This has not been our experience. When our ponds are forming ice at the
surface (coldest place), the bottom can be anywhere from 39 to 42 degrees.
Nothing but a small surface pump (or air stone) runs to keep a hole in the
ice. There is no current to mix the water and disrupt natural
stratification or disturb the hibernating fish.
--
McKoi.... the frugal ponder...
~~~ }<((((o> ~~~ }<{{{{o> ~~~ }<(((((o>

[George]

"Reel McKoi" > wrote in message
...
>
> "George" > wrote in message
> news:NuK4e.6628$g65.5582@attbi_s52...
>>
>> "Reel McKoi" > wrote in message
>> ...
>> >
>> > "ba5416" > wrote in message
>> > ...
>> >> The ice came off the pond a week or so ago. Found several fish floating
> on
>> >> the surface and several on the bottom. Pond is about a 1000 ga, 4ft
> deep
>> > at
>> >> the deep end. Pond has been in place for 4 years now with no problems.
> I
>> >> leave the pump running 24/7/365, turn the fountain off and leave the
>> >> waterfall run to keep things open.
>> >> Did the water quality tests once I found the dead fish. Everything was
>> > OK.
>> >
>> > $ You didn't allow the fish to find the "warm spots" at the bottom of
> the
>> > pond and rest for the winter. The current and cold probably killed
> them.
>> > Just about everyone in a cold climate turns the waterfalls etc off to
> allow
>> > this natural rest period - and so that the water can do it's natural
>> > conversion (cold at the top, warmer and still at the bottom.)
>>
>> I see that you flunked thermodynamics. Cold water sinks. Warm water
> rises.
> ==========================
> Excuse me,.... not in the winter. That's why ICE forms on top first - and
> works it's way down. My ponds stay around 40 F at the bottom when the
> surface is 32 and freezing. Looks like YOU flunked thermodynamics.....
> --

I guess you didn't read my response to Elaine:

I was waiting for someone to bring this issue up. It was discussed at length
last fall. In an effort to see how this affects shallow garden ponds, I
conducted a little experiment, measuring the water temperature at the surface,
and comparing it with water at the bottom (45").

Starting with autumn, let's see how the pond changed into the winter. The water
at the surface started out in October at 42°F. The first frost and cold wind
lowered the surface layer and it sank, while the warm water rose and replaced it
and was chilled in turn. This circulation process (which is typical of most
temperate bodies of water), continued until all the water reached 39.2°F, at
this temperature water is at its heaviest. Normally, any cooling beyond 39.2°F
does not sink, instead forms a thin layer at the surface because of the local
geothermal gradient, which will warm any water that is
below the frost line. However, with shallow ponds, the cold water can continue
to sink (especially if the pond is not dug below the frost line), and cause the
pond to continue to cool, and if this process continues (if the air temperature
remains below freezing for a significant period of time), the pond can freeze
completely to the bottom.

When the weather is cold enough, especially with low wind chill, the surface
freezes at (32°F). Freezing at the surface helps to stop the circulation, and
the warmer
water will stay at and below the frost line. Interestingly, when my pond
started to freeze (it only froze slightly on the very ends because I use a
de-icer), the fish didn't stay on the bottom, but hovered just below the ground
surface (my pond is 18" above ground, and 27" below ground, so they hovered at
about 18-20" below the water surface). In other words, they stayed about a
third of the way down in the pond. If it was significantly warmer at the
bottom, and warmth was of great concern to them, one would think that they would
have stayed at the bottom. This was not the case.

Before the ice began to form, but while the air temperature was still dropping,
the water at the bottom continued to drop until it reached a temperature of
34-35 degrees, at which time it stabilized. This was about the same temperature
as the water just below the surface (about 4 inches). It never dropped below
this temperature range except at the iar/water interface. When the temperature
was just above freezing, both the surface and the bottom water stayed around
34-36 degrees. The point is that unless a garden pond is dug well below the
frost line, you are not likely to see much of the stratification you normally
would see. This is why ponds that are not dug below the frost line can and do
freeze solid during a cold winter.

[Derek Broughton]

Reel McKoi wrote:

> "George" > wrote in message
> news:J5M4e.15943$Vx1.13708@attbi_s01...
>> Starting with autumn, let's see how the pond changed into the winter.
>> The
> water
>> at the surface started out in October at 42°F. The first frost and cold
> wind
>> lowered the surface layer and it sank, while the warm water rose and
> replaced it
>> and was chilled in turn. This circulation process continued until all the
> water
>> reached 39.2°F, at this temperature water is at its heaviest. Normally,
> any
>> cooling beyond 39.2°F does not sink, instead forms a thin layer at the
> surface
>> because of the local geothermal gradient, ...........
> ============================
> This has not been our experience. When our ponds are forming ice at the
> surface (coldest place), the bottom can be anywhere from 39 to 42 degrees.
> Nothing but a small surface pump (or air stone) runs to keep a hole in the
> ice. There is no current to mix the water and disrupt natural
> stratification or disturb the hibernating fish.

That's pretty much what George said :-) If water's densest at 39.2°F, then
(at least in water deep enough to stay liquid and have a noticeable
temperature gradient) the water should never get colder than that but could
be warmer.
--
derek

[kathy]

Fish health is not my area but...
- did you do anything different this year than
the previous winters?
Such as a fall clean out, the waterfall running during
the winter. That would probably be where to start looking.

One year I went into winter with a huge growth of anacharis
in the pond, so much that sometimes I could never see the fish. By
winters end it was all gone! I was sure surprised, and I assumed the
fish (a lot of koi at the time) chowed down on it sometime during that
period.

Also your fish have probably mulitplied in the time you've
had them. What may have worked for the orginal fish load
may not be working for the current fish load.

kathy :-)

[Reel McKoi]

"Derek Broughton" > wrote in message
...
> Reel McKoi wrote:
>
> > "George" > wrote in message
> > news:J5M4e.15943$Vx1.13708@attbi_s01...
> >> Starting with autumn, let's see how the pond changed into the winter.
> >> The
> > water
> >> at the surface started out in October at 42°F. The first frost and cold
> > wind
> >> lowered the surface layer and it sank, while the warm water rose and
> > replaced it
> >> and was chilled in turn. This circulation process continued until all
the
> > water
> >> reached 39.2°F, at this temperature water is at its heaviest. Normally,
> > any
> >> cooling beyond 39.2°F does not sink, instead forms a thin layer at the
> > surface
> >> because of the local geothermal gradient, ...........
> > ============================
> > This has not been our experience. When our ponds are forming ice at the
> > surface (coldest place), the bottom can be anywhere from 39 to 42
degrees.
> > Nothing but a small surface pump (or air stone) runs to keep a hole in
the
> > ice. There is no current to mix the water and disrupt natural
> > stratification or disturb the hibernating fish.
>
> That's pretty much what George said :-) If water's densest at 39.2°F,
then
> (at least in water deep enough to stay liquid and have a noticeable
> temperature gradient) the water should never get colder than that but
could
> be warmer.
> --
> derek
=====================
Whoops,.. I should have read it closer. Thanks for bringing that to my
attention. ;-)
--
McKoi.... the frugal ponder...
~~~ }<((((o> ~~~ }<{{{{o> ~~~ }<(((((o>

[Reel McKoi]

"George" > wrote in message
news:z4T4e.10070$yg7.7550@attbi_s51...
> I guess you didn't read my response to Elaine:

## Sometimes my newsreader is behind.

> I was waiting for someone to bring this issue up. It was discussed at
length
> last fall. In an effort to see how this affects shallow garden ponds, I
> conducted a little experiment, measuring the water temperature at the
surface,
> and comparing it with water at the bottom (45").
>
> Starting with autumn, let's see how the pond changed into the winter. The
water
> at the surface started out in October at 42°F. The first frost and cold
wind
> lowered the surface layer and it sank, while the warm water rose and
replaced it
> and was chilled in turn. This circulation process (which is typical of
most
> temperate bodies of water), continued until all the water reached 39.2°F,
at
> this temperature water is at its heaviest. Normally, any cooling beyond
39.2°F
> does not sink, instead forms a thin layer at the surface because of the
local
> geothermal gradient, which will warm any water that is
> below the frost line. However, with shallow ponds, the cold water can
continue
> to sink (especially if the pond is not dug below the frost line), and
cause the
> pond to continue to cool, and if this process continues (if the air
temperature
> remains below freezing for a significant period of time), the pond can
freeze
> completely to the bottom.

## Yes. I agree. That's why we try and dig them so at least one part of
the bottom is below the frost line, even here in TN.

> When the weather is cold enough, especially with low wind chill, the
surface
> freezes at (32°F). Freezing at the surface helps to stop the circulation,
and
> the warmer
> water will stay at and below the frost line. Interestingly, when my pond
> started to freeze (it only froze slightly on the very ends because I use a
> de-icer), the fish didn't stay on the bottom, but hovered just below the
ground
> surface (my pond is 18" above ground, and 27" below ground, so they
hovered at
> about 18-20" below the water surface). In other words, they stayed about
a
> third of the way down in the pond. If it was significantly warmer at the
> bottom, and warmth was of great concern to them, one would think that they
would
> have stayed at the bottom. This was not the case.

## I was told that aside from warmth the supply of oxygen is also important
to them. But all things being equal they will rest on the bottom and expend
less energy than hovering or fighting a current, any current, all winter.
Mine stay on the bottom barely moving through the winter. In the shallow
pools they stay under the heaters.

> Before the ice began to form, but while the air temperature was still
dropping,
> the water at the bottom continued to drop until it reached a temperature
of
> 34-35 degrees, at which time it stabilized. This was about the same
temperature
> as the water just below the surface (about 4 inches). It never dropped
below
> this temperature range except at the iar/water interface. When the
temperature
> was just above freezing, both the surface and the bottom water stayed
around
> 34-36 degrees. The point is that unless a garden pond is dug well below
the
> frost line, you are not likely to see much of the stratification you
normally
> would see. This is why ponds that are not dug below the frost line can
and do
> freeze solid during a cold winter.

## Gotcha! :-)

--
McKoi.... the frugal ponder...
~~~ }<((((o> ~~~ }<{{{{o> ~~~ }<(((((o>

[ba5416]

I left the waterfall run like I have every year since I put it in and have
had no problems before with winter kill. When I cleaned out the pond in late
Aug/early Sept there were 45 fish. Out of the 45 perhaps 25 of them were 1"
or less, ten of them were 1.5" long, 10 of them were 2" long, the other 5
are at least 4". Out of all that the fish that have survived 4 are the
bigger ones with the exception of perhaps 3 or 4 smaller ones (1") The three
biggest ones that are left have been in the pond since the first year. One
note on the whole discussion about water temps. The filter sits up one
level from the absolute bottom. In other words it sits up about 8" from
bottom. The filter has sat here since day one also.
"kathy" > wrote in message
ups.com...
> Fish health is not my area but...
> - did you do anything different this year than
> the previous winters?
> Such as a fall clean out, the waterfall running during
> the winter. That would probably be where to start looking.
>
> One year I went into winter with a huge growth of anacharis
> in the pond, so much that sometimes I could never see the fish. By
> winters end it was all gone! I was sure surprised, and I assumed the
> fish (a lot of koi at the time) chowed down on it sometime during that
> period.
>
> Also your fish have probably mulitplied in the time you've
> had them. What may have worked for the orginal fish load
> may not be working for the current fish load.
>
> kathy :-)
>

[Andy Hill]

"ba5416" > wrote:
>The ice came off the pond a week or so ago. Found several fish floating on
>the surface and several on the bottom. Pond is about a 1000 ga, 4ft deep at
>the deep end. Pond has been in place for 4 years now with no problems. I
>leave the pump running 24/7/365, turn the fountain off and leave the
>waterfall run to keep things open.
> Did the water quality tests once I found the dead fish. Everything was OK.
>I did a major cleanout of the pond last Aug by netting all the fish (about
>40 from 5" down to 1/2", removing the plants, draining the water and sucking
>up all the black ooze that was on the bottom. Replaced all the water, (we
>are on a well), did water samples, replaced the fish, fed the fish until
>water temps dropped below 55 and waited for winter. Is it possible that with
>the cleaning there were not as much food for them to forage on over the
>winter? I have had more fish die in the past couple of days. The three
>original fish from the beginning are still there and getting active. I
>netted a couple of the smaller ones that were born in the pond and do not
>see any issues with the gills or scales. I did a basic autopsy on one of the
>dead fish and the stomach was totally empty.
>
>I am stumped with this one. Did they starve or is there something else going
>on.
>
Starvation doesn't seem real likely -- fish shouldn't have to eat as long as the
water is cold.

Anybody spraying nearby trees or lawn with pesticide? Poisoning tends to kill
the small fish before the big ones.

[George]

"Reel McKoi" > wrote in message
...
>
> "George" > wrote in message
> news:J5M4e.15943$Vx1.13708@attbi_s01...
>> Starting with autumn, let's see how the pond changed into the winter. The
> water
>> at the surface started out in October at 42°F. The first frost and cold
> wind
>> lowered the surface layer and it sank, while the warm water rose and
> replaced it
>> and was chilled in turn. This circulation process continued until all the
> water
>> reached 39.2°F, at this temperature water is at its heaviest. Normally,
> any
>> cooling beyond 39.2°F does not sink, instead forms a thin layer at the
> surface
>> because of the local geothermal gradient, ...........
> ============================
> This has not been our experience. When our ponds are forming ice at the
> surface (coldest place), the bottom can be anywhere from 39 to 42 degrees.
> Nothing but a small surface pump (or air stone) runs to keep a hole in the
> ice. There is no current to mix the water and disrupt natural
> stratification or disturb the hibernating fish.

The wind keeps the convection going, which is why when it is blocked by ice at
the surface, the convection stops. Again, how this affects a body of water
depends largely on its depth. The shallower it is, the less likely it is to
stratify, and the more likely it is to freeze solid. This becomes especially
noticable when the pond is not dug below the frost line where the geothermal
gradient can positively affect the temperature.

[George]

"Derek Broughton" > wrote in message
...
> Reel McKoi wrote:
>
>> "George" > wrote in message
>> news:J5M4e.15943$Vx1.13708@attbi_s01...
>>> Starting with autumn, let's see how the pond changed into the winter.
>>> The
>> water
>>> at the surface started out in October at 42°F. The first frost and cold
>> wind
>>> lowered the surface layer and it sank, while the warm water rose and
>> replaced it
>>> and was chilled in turn. This circulation process continued until all the
>> water
>>> reached 39.2°F, at this temperature water is at its heaviest. Normally,
>> any
>>> cooling beyond 39.2°F does not sink, instead forms a thin layer at the
>> surface
>>> because of the local geothermal gradient, ...........
>> ============================
>> This has not been our experience. When our ponds are forming ice at the
>> surface (coldest place), the bottom can be anywhere from 39 to 42 degrees.
>> Nothing but a small surface pump (or air stone) runs to keep a hole in the
>> ice. There is no current to mix the water and disrupt natural
>> stratification or disturb the hibernating fish.
>
> That's pretty much what George said :-) If water's densest at 39.2°F, then
> (at least in water deep enough to stay liquid and have a noticeable
> temperature gradient) the water should never get colder than that but could
> be warmer.
> --
> derek

But when the pond is above the frost line in temperate regions, it is less
likely to stratify significantly, if at all, and will freeze.

[George]

"Reel McKoi" > wrote in message
...
>
> "George" > wrote in message
> news:z4T4e.10070$yg7.7550@attbi_s51...
>> I guess you didn't read my response to Elaine:
>
> ## Sometimes my newsreader is behind.
>
>> I was waiting for someone to bring this issue up. It was discussed at
> length
>> last fall. In an effort to see how this affects shallow garden ponds, I
>> conducted a little experiment, measuring the water temperature at the
> surface,
>> and comparing it with water at the bottom (45").
>>
>> Starting with autumn, let's see how the pond changed into the winter. The
> water
>> at the surface started out in October at 42°F. The first frost and cold
> wind
>> lowered the surface layer and it sank, while the warm water rose and
> replaced it
>> and was chilled in turn. This circulation process (which is typical of
> most
>> temperate bodies of water), continued until all the water reached 39.2°F,
> at
>> this temperature water is at its heaviest. Normally, any cooling beyond
> 39.2°F
>> does not sink, instead forms a thin layer at the surface because of the
> local
>> geothermal gradient, which will warm any water that is
>> below the frost line. However, with shallow ponds, the cold water can
> continue
>> to sink (especially if the pond is not dug below the frost line), and
> cause the
>> pond to continue to cool, and if this process continues (if the air
> temperature
>> remains below freezing for a significant period of time), the pond can
> freeze
>> completely to the bottom.
>
> ## Yes. I agree. That's why we try and dig them so at least one part of
> the bottom is below the frost line, even here in TN.

The frostline differs from locality to locality. Here in North-Central
Kentucky, the frost line is 22". Although my pond is 45" deep, only 27" of it
is below ground, making the bottom only 5" below the frost line. This is why I
don't see stratification. I recieve just enough warmth from the ground to keep
the pond from freezing solid in the coldest winters (actually, I couldn't dig
any deeper because of a hardpan that exists here below 27", which makes hand
digging exhausting). The pond is also shaded from strong wind because it abutts
a tall wooden privacy fence.

>> When the weather is cold enough, especially with low wind chill, the
> surface
>> freezes at (32°F). Freezing at the surface helps to stop the circulation,
> and
>> the warmer
>> water will stay at and below the frost line. Interestingly, when my pond
>> started to freeze (it only froze slightly on the very ends because I use a
>> de-icer), the fish didn't stay on the bottom, but hovered just below the
> ground
>> surface (my pond is 18" above ground, and 27" below ground, so they
> hovered at
>> about 18-20" below the water surface). In other words, they stayed about
> a
>> third of the way down in the pond. If it was significantly warmer at the
>> bottom, and warmth was of great concern to them, one would think that they
> would
>> have stayed at the bottom. This was not the case.
>
> ## I was told that aside from warmth the supply of oxygen is also important
> to them. But all things being equal they will rest on the bottom and expend
> less energy than hovering or fighting a current, any current, all winter.
> Mine stay on the bottom barely moving through the winter. In the shallow
> pools they stay under the heaters.

Yes, O2 is very important to fish in the winter, especially Koi, or if you have
a lot of fish in the pond. I aerate the pond during the winter. The only fish I
have that goes to the very bottom in winter is my albino channel cat, and he
rarely stays there for long periods of time, even in winter.

>> Before the ice began to form, but while the air temperature was still
> dropping,
>> the water at the bottom continued to drop until it reached a temperature
> of
>> 34-35 degrees, at which time it stabilized. This was about the same
> temperature
>> as the water just below the surface (about 4 inches). It never dropped
> below
>> this temperature range except at the iar/water interface. When the
> temperature
>> was just above freezing, both the surface and the bottom water stayed
> around
>> 34-36 degrees. The point is that unless a garden pond is dug well below
> the
>> frost line, you are not likely to see much of the stratification you
> normally
>> would see. This is why ponds that are not dug below the frost line can
> and do
>> freeze solid during a cold winter.
>
> ## Gotcha! :-)
>
> --
> McKoi.... the frugal ponder...
> ~~~ }<((((o> ~~~ }<{{{{o> ~~~ }<(((((o>
>

[Derek Broughton]

George wrote:

> But when the pond is above the frost line in temperate regions, it is less
> likely to stratify significantly, if at all, and will freeze.

Right, I was trying to figure how to quantify "deep enough". Obviously,
below the frost line would be important :-)
--
derek