Robin, your best bet would be to use a device that works only as needed to keep ice from forming around it. It's called a de-icer. Your stock tank heater works continuously to raise the temp level of the entire pond and costs a lot more to operate.

Another method is to use a bubbler. I use a fairly large one for my 1000 gallon pond. I have a de-icer but haven't needed it as long as the bubbler is working. The moving water eliminates or reduces so-called dead zones, too.

You don't need a huge area cleared of ice. Just a small hole works fine.

Actually, raising the temp of the entire pond is probably more harmful to fish health than allowing the water temp to stay low. The fish are being encouraged to come out of their winter torpor too often with the warmer water.

Sleepless, Please tell me about the de-icer. Can I leave it on for 5 weeks straight? Does it use a lot of electricity? Where do they sell them?
Also, how can I figure the number of gallons in my tank?
Thanks!

There are several sites that help you determine the volume of your pond. Just do a search on your browser for pond volume calculator.

You should leave a de-icer on all the time since it works on a thermostat. It only uses electricity when it comes on so operating costs are minimal unless you are in the arctic circle. Since it is not attempting to raise the level of all the water all the time the cost would be far less than your heater. The area it melts or keeps from freezing is usually only a sliver, maybe a quarter of an inch, around the de-icer. It stays on the surface rather than sinking like your heater. In Pennsylvania it is unlikely you would have a problem if you plugged it in before the ice actually formed. In zone 5 I have never had the ice to be more than 6 inches and that was in sub zero cold. There are several on the market and readily available online.

Cost is pretty variable. I can't judge brands simply because I have not needed to buy that many. One I purchased at a feed store 20 years ago in northern Wisconsin and the one I have now that I have not needed, I got at Menards year end sale. I have seen them at Tractor Supply, Fleet Farm and various pond shops. If I remember correctly they are more expensive than the heaters since they require the thermostat.

If you don't want to spend that much you can make your own. I did that the first few years after I dug this pond. I used a refrigerator or rough duty lightbulb, the necessary wiring and a Roughtote storage box with a hole in the bottom and a float or raft made from some scrap Styrofoam board. There are plans somewhere using a search if you are curious. It cost about $10.00 with the scraps and odds and ends I had on hand. A piece of cheesecloth stretched over the hole keeps the bulb from shattering or if it does,keeps the glass out of the water. I used Great Stuff as an adhesive. The only problem was it was ugly!

On the otherhand, if you use a bubbler, a de-icer isn't likely to be needed at all. My bubbler and 2 airstones go all year long for very low cost and effort. drh1, Professor David, makes an excellent case for a bubbler by itself to zone 4. The entire very excellent thread is linked below and gives more info than I can give in this post but this is his argument.

"Posted by drh1 z4 VT (My Page) on Fri, Aug 20, 10 at 17:55
Hi Jenny,
First, the more important questions: Nope, leaf peeper season hasn't started yet! That's usually the end of September - first week in October (for the Champlain Valley). Already many motels and Hotels are booked solid. Shoveling snow?? When one is retired it is irrelevant. You get up, you look out, you say "oh, it snowed last night; looks like 18". Isn't it pretty". You have another cup of tea/coffee; go back to bed or not. Wait until Spring to shovel out. Not-a-problem!
Now to your questions: First let's deal with some heresy: a hole in your ice DOES NOT MATTER! Gasp! WHAT DID HE SAY??? Nope, it's all about providing a surface for gas exchange. IF... you're using a heater, a light bulb, stock tank heater, etc. then it IS about keeping a hole open since that is the only surface over which the gas exchange can take place. However, with an aerator the gas exchange surface is in the bubbles...NOT in the hole that may or may not be in the ice. All that air you pump in there has to go somewhere otherwise you'd have the equivalent of one of those air-hockey games only with an "ice puck" floating on an air cushion! But that doesn't happen...the air finds a way out - through a crack, through the edges, though a hole. So if it "domes over"...so what? The air is STILL finding a way out. And because you are pumping air in it is the aggregate surface area of all those bubbles that is providing the surface area for gas exchange...and it is HUGE! With a stocktank heater in our neighborhood with our winters you might get a few square feet for a hole although at -20°F you might find it disappears! But the aeration approach continues to put out 10's of square feet of surface area every minute!!! As a result not only will you keep more than enough oxygen in there (not really that much of a problem given that the metabolisms for the fish are almost non-existent as well as the microbes involved in consuming organics - and oxygen - aren't doing too much...but still not exactly zero!) but you will be stripping out ammonia and carbon dioxide and other gases you wouldn't want trapped under the ice. This is the real benefit of the approach to using aeration.

As to the plastic tent? Not sure it does too much although it does allow me to see the hole for an extra couple of months. But I've had it get ice inside, even an inch or so ABOVE the water level... but still not really relevant as long as the aerator/bubbler is doing it's thing. Note the ice auger in one picture...I went out to check one fine February day (think high of -10°F!). Couldn't really see a hole in the ice under the teepee. Drilled a hole and looked...yep, everything was working fine. But the ice melted out under the teepee more about a month before it melted out of the pond so there is some solar benefit. The real purpose of the floating thing is to hold the aerator above the bottom of the pond.

As to adding a stock tank heater on the coldest days?? I wouldn't bother. If you lived in zone 6 or 7 you might have some impact on the temperature in or around the heater but in my zone (and I suspect yours) adding even a 2500 watt heater is akin to performing a particular bodily function into the wind! Yes, it probably will melt out a hole, but once the heater is down near the bottom of the pond with an outside temperature of say -15° or -25°F I suspect there will be no measurable impact on water temperature. Having a heater on hand, however, does provide a way to work on thawing out a line if it develops an ice plug. I don't own a heater since, as mentioned above, I use other approaches for that problem.

Like I said.. it works for me and as posted in the URL above it works for other folks as well. The problem is to understand that you are not really trying to HEAT the water to some acceptable limit but rather maintain a surface area open for gas exchange. I like cheap. I like what works...and so far, over several years, it has worked for me. The biggest factor will be whether your pond depth and volume will provide the heat transfer necessary to keep a water layer below the ice, i.e., making sure the whole (no pun intended!) thing doesn't freeze up!
---David"

I definitely recommend you read the entire discussion. Anything David or Horton write is pure gold and it should reassure you.

Here is a link that might be useful: Complete discussion on ice holes for ponds

This assumes you have electricity available:

A bubbler made from a double port air pump placed inside a covered plastic container to keep it dry. Cut two holes and the end of the container for the tubing to come out and sink the two tubings twined together with airstones at each end and place about 12" under the surface. Plug in the pump and the bubbles will keep a small hole open that will get smaller or larger depending on the weather. If it freezes over you will still get air bubbles that will weezle their way out at some point near edges of the pond or where plant stems break the surface, etc. Cut a small hole in the other end of the container to fish the pump electric plug to an outlet. Make sure all is covered with something. I used a piece of rubber liner but don't make it air tight obviously as the air pump needs air:-)

You could use a Thermopond deicer which is about 100 watts. I had one for two years and then it pooped out on me. It kept a small hole in the ice and I would see the fish crusing the area under it.

Right now I use nothing except my external filter with two jets of water coming out of it with a 2400 gpm pump at the other end of the pond. It never freezes at my zone 7 with that water falling in so fast. You never know though - one could get a freak, sub-zero freeze.

I personally think fish can survive for a short while if the water is deep and you don't have an overload of fish and the pond is large. Also, leave plants, if you have them, sticking out of the surface of the water as much as possible - hollow stem ones if you can.

You can also sink a 500gpm pump just under the surface and that will keep it open. Moving water doesn't freeze except when very cold for a long time. I've seen waterfalls freeze but that was way north during a sub-artic freeze.

What is your frost line? Mine is 22" in zone 7. Not supposed to freeze below that point.

Thank you for your advice. I did purchase an aerator/bubbler - Laguna Aeration Kit which was recommended by a friend. I understand that I should put it in some kind of waterproof container any more advice on this? I hope I made the right decision.

Robin - I used a shoebox sized container made of plastic with a fitted lid. Any variety type store has them.

I cut out a small area on one end for the tubing to exit out to the pond and another small hole on the other end for the electric wire and plug which was plugged in right there as my electric source is pondside. The lid was also used.

The covered box with air pump inside was loosely wrapped with a piece of scrap rubber liner with a brick on top to keep out the snow/rain/wind. I set the whole rig on top of a brick paver also to keep it off the ground. I used a cheap $10 double port air pump from Wal-mart.

For tubing look for silicone as it withstands colder temperatures than plain pastic tubing. Also, I suggest using back-flow preventers for the tubing to be on the safe side. You can buy those where you get the clear, silicone aquarium tubing (if that is the tubing you decide to use). Tubing diameter depends on the size of your air port on the kit you bought. Now that I think of it perhaps your kit has everything you need except the box to put it all in and a secondary cover to loosely wrap it since you will have holes at both ends of your box.

Hi Robin,

I wanted to add my two cents. I'm the Jenny that Professor David was responding to in the above quoted post. I followed the good professor's advice last winter and my fish survived just fine! I had 2 shubunkins and 7 koi last year and they are still going strong this winter.

I understand your worries; I felt the same way last winter. When the pond iced over and then snow covered the ice I couldn't even hear the aerators bubbling away anymore and was positive I'd find fish-sicles in the spring. Nope, not the case.

Put in an aerator maybe a de-icer too if it helps you sleep better and enjoy your time away, the fish will be fine!