It is not the size of the bubbler that is important. You are not trying to
achieve filtration by air driven under gravel filters, you are trying to
keep the top surface of the water disturbed to prevent freezing over. Any
of the pumps will work, just put a big airstone on the line, suspend the
airstone a few inches from the top, and let it do the work of a heater.
--
RichToyBox
http://www.geocities.com/richtoybox/index.html

"Rick" wrote in message
ink.net...
Tom
How big of a bubbler do I get? Looked a Wally Word and the biggest one is
for a 40 to 60 gal tank. my pond is give or take 1200 gal.

"Tom L. La Bron" wrote in message
...
Rick,

I don't have that much problem with total ice cover and
according the Farmer's Almanac this winter is suppose
to be mild in my region, but there have been winters
with total solid ice cover.

Over the years I have checked trough de-icers and they
usually run 1,000 to 1,500 watts and the thermostats
that some of them have turn on between 38 degrees F. to
34 degrees F. depending on the brand. Needless to say,
the cost of running one can be high, so I have used
airstones.

The airstone may not keep a hole in the ice but it will
cause an escape for the air through the ice which is
what needed. One of the years when the ponds froze
over sold I came out and told myself, "what a waste,"
because there was no hole. Upon closer inspection I
found that the air was making its way up through
channels created as the ice froze. One of the
important things that you have to remember when using
an airstone is to have the airstone just below where
the thickness of the ice will accumulate, you don't
want to disturb the water layers at the bottom of the
pond, so keep it high in upper level of your pond. I
have switched over to an air blower so my airstones
this year will only be about 6 inches below the surface
of the water, which for me is more than enough.

Good luck with what ever technique you decide to use.

HTH

Tom L.L.

Rick wrote:
I have bin told to just put one of those heaters that the farmers use
to
keep fresh water for there cattle from freezing in to my pond. They
have a
built in thermostat and only turn on when the water reaches 33 or 34
degrees. I have also bin told that you should not let the pond freeze
over
because of the gas build up and not the lake of oxygen. Are you
saying
that
I sill should put in a Bubbler?




"George" wrote in message
.. .

"Ka30P" wrote in message
...

Roark did a bit on water and winter in response to a question and it

makes a

pretty interesting read.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~
From: Roark7
Subject: Bubbling bottoms and super cooling
Date: 1997/10/31

David Swarbrick wrote:


Bubblers are recommended for maintaining an ice free portion of a
pond
over winter, and maintaining good oxygen levels. I have also seen it
suggested here that it should not be placed on the bottom of the
pond,
but raised so that the circulation it induces does not disturb the
water
at the every bottom because this merely results in the very cold
water
by the ice being distributed all over.

I question this.

Yep... And I don't blame you one bit. I had the same doubts and

voiced the

same arguments that you shortly share because it *is*

counter-intuitive...

until you start looking hard.

Actually, if your pond is deep, like mine (45 inches or more), the

circulation,

which goes from bottom to top, will draw the residual warmth in the
ground

below

the frost line to the upper levels of the pond, and moderate the water
temperature. I ran a bubbler from the bottom all winter last year and

only had

ice two days (less than 1/8 inch thick, at that, and only on one end).


First, warm water rises, and cold water sinks. The water at the
bottom
will always circulate if there is a temperature difference. Frozen
water
floats. I suppose there must be a point just before water freezes
where
the situation turns on its head, but I assume also that this is only
at
the point very near freezing.

I had major questions about the physics aspect of this whole "winter

pond"

thingy as well. I did some asking and a bit of research and came up
with

three

things which cause the inverse stratification effect. These are, in

ascending

order of importance:

- The native heat of the earth
- The physics of water going from a liquid to a solid
- Surface cooling due to winds and cold air.

I'll rattle through each contributing effect in detail below:

- Heat of the Earth:
It turns out that the earthern bottom of a 4-foot deep pond stays
right

around

34-38 degrees even though the outside air temperature drops much
lower.

The

simple reason for this is the Earth is slightly exothermic.
As you dig down
you hit a point where more heat is being released by the earth than
can

be

pulled-away by wind, night sky, etc. This is why you bury water
pipes

below

the "frost line". This heating effect is small in ponds, but it *is*

there.

The earth *is* pumping a bit of heat energy into it all the time.
The

other

effects (below) tend to magnify this effect into something useful by

keeping

this slightly warmer water on the bottom.

I will add here that the residual heat of the earth is called the

geothermal

gradient, and varies from place to place, and increases with depth.
But

at

shallow depth, it is affected by surface temperatureand wind chill.
For
instance, at the latitude where I live (38 degrees), the air in a cave

stays in

the vicinity of 54 degrees F, depending on air currents within the
cave,

which

depend on the connectivity of cave passages, and the number of surface
entrances, all of which can affect the transfer the heat to the

surface,and visa

versa. Travel north of this latitude, and the temperature is lower.

Travel

south of this latitude and the temperature is higher. With regard to

ponds, the

surface temperature has an effect on the soil, but only to within a

certain

depth. That depth is called the frost line. Below that depth, the
soil

will

not freeze, but will retain it's residual warmth, and increase with

increasing

depth. The frost line varies with latitude. At my latitude, the
frost

line is

at 22 inches. In order to keep buried utilities from freezing (such
as

water

lines), the local building codes required the utilities to be buried
six

inches

below the frost line, at 28 inches. If you live at 38 Degrees north

latitude,

and your pond is 45 inches deep, then the bottom 17 inches will not
freeze
(unless, of course, you have an abnormally cold winter, in which case,

your pond

can actually freeze solid, but this is rare in most cases). Lat year
my

pond

only had a small surface crust for two days, and then stayed ice free
the

rest

of the winter.


- Physics of Water:
It turns out that water doesn't move upwards because it is "warm" nor

sink

when
it becomes "cold". A little thought reveals this behavior is
strictly
a
function of density. Warmer water *tends* to be less dense so it

rises... but

this isn't gospel. An interesting kink in the water density -vs-

temperature

curve shows-up just prior to 32 degrees F. At the pre-freezing
point

(32.8

F), water undergoes a major density change. As it cools it becomes

*less*

dense than water which is just a fraction of a degree warmer. This

difference

is fairly large. Being lighter than the surrounding water,
near-freezing

water

*rises*. (This is one reason frozen pipes tend to burst. The
density

of the

water decreases, the mass stays the same, so the result is volumetric
expansion which splits pipes with ease.) The degree of final
bouyancy

is

controlled to a large part by the dissolved oxygen content of the
water.

The

more dissolved O2, the greater the expansion once the freezing point
has

been

reached. Since water at the *top* of the pond tends to have a
greater

O2

concentration, this further contributes to stratification.

Near-freezing

water moves toward the surface, and then, having reached the surface,

freezes

completely.

Unless, of course, you draw warmer water up from below, which is why I

place the

air stone at the bottom in the winter. Some have suggested that
drawing

the

warmer water from the bottom to the top will cause the temperature of
the

water

at the bottom to drop. But that doesn't happen if the pond is below
the

frost

line because the surrounding soil will release it's residual heat into
the

water

as the warmer water is drawn towards the surface. Of course, if your
air

supply

is outside, and the temperature gets very cold, pumping that cold air
into

the

water could affect the water temperature. The overall temperture of
the

pond

may drop slightly, but usually not enough to adversely affect the fish

unless

the air temperatuere stays below freezing for a long period of time
(in

which

case, you might consider keeping your air pump indoors and running the

hose out

to the pond. I know a guy who has installed a buried air hose to his
pond

from

his basement, where his air pump is located. So in the winter, he is

actually

pumping heated air into the pond).


- Surface Cooling Effects
This one is pretty obvious, but its worth restating to put it in

context.

Given a sub-freezing day and a brisk wind, its a simple matter to
pull

more

heat from the top layer of water than can be replaced by natural

convection.

Once the top starts to freeze, heat loss to ambient and basic water

physics

insures the top will *stay* cooler than the bottom. If this wasn't

true,

you'd never see a thin coat of ice.... the pond would instead just
hit
a

point

where the entire thing suddenly became a solid chunk of ice.


It seems to me that if the air being pumped in is warmer anyway (in
my
case, from inside an unheated shed), then the balance will be about
right.

Your idea about pumping warm air into the water isn't a bad one, but
it

will

take a lot of warm air to make a dent in the ponds temperature....
far

more

than you could reasonably produce.

That is true. However, as I stated above, pumping cold air into the
water

can

adversely affect the water temperature. So, the warm air won't heat
the

water,

but will simply prevent it from making the water colder than cold air

will.

Pumping a large amount of air in would
also create currents which the fish would need to fight or at least

adjust

for. Hibernating fish are in no position to do this and forcing them

into

this situation uses energy they will need during the rest of the
winter.

For keeping a hole in the ice however, you could likely use this

warm-air idea

to your benefit. Put an airstone a foot under the water and run warm

air to

it. Bear in mind that you will lose lots of heat in just a short
run

between

your shed and the airstone.

An alternative would be to purchase an electric deicer for about
$50-$60:

http://www.pondsolutions.com/pond-heaters.htm


Also if the problem with water under ice is the lack of oxygen and
build
up of waste products under the ice, then the more chance the bubbler
has
to oxygenate the water and take away the foul water the better.

Whether you use a de-icer or not, it is always a good idea to add air
to

the

pond in the winter time for the reasons you state above.


The oxygen demands of fish near the freezing point are very, very
low.

This

is
a good thing because I've got a feeling there isn't much oxygen

available once

you near the peak of winter. Fortunately, decay and decomposition of

wastes

by bacteria has nearly stopped as well which relieves a decent
portion

of the

oxygen load. Very little oxygen is needed in a winter pond.

Unless it freezes over, in which case, there is no oxygen exchange,
and

the fish

could die.


During a really *cold* winter, I think the idea of a full-blown
bubble

system

would tend to upset a natural balance which Nature clearly went out
of

her way

to establish. Having said that however, I can see a very definite

*benefit*

to using such a system as the air temp starts to push into the upper

30's and

40's. By introducing additional air and inducing water motion,
you'd

be

putting lots of needed oxygen into the water as well as helping the
pond

to

absorb ambient heat. Fish coming out of their winter sleep wouldn't
be
oxygen-stressed as well as being thin, worn and badly in need in of a

shower.

From what I'm given to understand, most fish have no problems

during the

actual *wintering*... its the *transition* from hibernation to normal
metabolism which gets them. Your bubbler could be a great tool
during

that

transition period.

It is also important to transition your fish to food that is easier to

digest

when preparing the pond for winter as the microbes in their gut that
helps

in

digestion will eventually go dormant.