Frank, no "Expert" here,I have just learned a few things over the years and offer them out for people to try or not try, as they please.
I kept a 100 gallon, 18" deep preformed pond from freezing up completely, by running a 500 GPH pump to move the surface water.
The pump was lifted up from the bottom of the pond onto a block at one end of the pond and the water from it, bubbled up to the surface keeping a hole open in the ice all winter long.
I did attach a short 1/2" pipe with a 45° fitting on it, to the pumps out port which sent a stream of water up and across the pond at and angle.
This kept most of the surface water moving and circulating around the pond. Don't worry about warnings of "Super Cooling" because you are moving and mixing the water as it is not that severe a problem as some people will have you believe.

Covering your pond over with a box or a tarp, also helps keep the wind from blowing across the pond's surface. And having an electric pond de-icer as a back up, in case the pump quits is a good idea.
Hope this helps.
"Horton"

Thanks Horton. My latest thought was basically exactly what you said. Thinking of picking up submersible pond de-icer to put on bottom of pond and placing my spare 325gph pump on one of the shelves of the pond. Putting a 90 deg elbow on the outlet so it would shoot the water out to the rest of the pond across the top of the pond.

I would "tent" your pond keeping the wind and snow off of it. Easily done with some 2x4s and heavy guage clear plastic. Get a fish tank air pump, some tubing and an air stone, get the $3.00 long ones. If you want to go all out add a horse trough de icer ring..about $12.00. Should not cost you over $50.00 total. BUT I am NOT anywhere near an expert, just letting you know what I do here in MI. z-5

I have a small pond, 18 - 20 inches deep. Zone five. I also have several maple trees. I've tried netting & covering to keep the leaves out to no avail and the pond mucks up. I bring in the fish and non-hardy plants and place into a large fish tank. Plants go in a plastic 'car-topper'under fluorescent lights. Pull the filter & pump. Come spring I attach a garden hose to the pump & filter and empty the pond. Wash it out, get all of the debris out and refill. Transfer the fish and plants when things get warm enough. Easier and cheaper for me to do that than keep it going all winter..

Just FYI: At the top of the main Ponds & Aquatic Plants page there are the Frequently Asked Questions (link). If you click on that the last one in the list is information from drh1 and others about making a couple of deicers. You could always try that.

I'm no expert either but I do very little to winterize my 9' x 12' (19" deep)pond here in Z5. I disconnect the pump from the waterfall, leave it running in the pond with the output port about 4" below the surface to keep the surface agitated to prevent freezing (sometimes the pond surface still freezes over but only for a couple of days during bitter snaps). My Koi/Shubunkin/Goldfish remain in the pond all winter (sometimes I see them moving below the ice!). I also leave the waterlilies and some of the margin plants (Marsh Marigolds) fully submerged below the ice.

I've tried different schemes to keep leaves and acorns out of the ponds with little success. This year I'm trying a 3/4" PVC frame covered with netting to see if I have better luck keeping the leaves out but I suspect next spring I'll be knee deep in the pond as usual removing leaves from the bottom.

This is the first year I've had frogs in the pond. I raised them from tads in the spring. When I originally built the pond I left large folds in the pond liner in the corners of the pond since I had read somewhere that frogs can over-winter by squeezing into these folds. Sounds good - we'll see. But I suspect they will successfully fend for themselves no matter what I do.

I've never lost a fish or a plant to winter-kill over the years with the above scheme (or lack of a scheme :-))

I'm in NY also. My yard is heavily wooded so I get a lot of leaves. I used to try to cover my pond with netting but that just weighed down with the leaves and sunk into the water. The last few years I've collected used window screens and door screens from an online group - freecycle I lay the screens over the pond (the door screens fit from end to end of the pond.)And the smaller window screens I connected to each other by drilling holes in the frames and connecting with plastic electrical tie wraps. I can leave the screens on top, or if I feel like it, I'll put my netting on tops of the screens for extra protection. The rigidity of the screens keep the net from sinking into the pond under the weight of the leaves. Works pretty nicely. And its easy on, easy off. I take my 5000 gph pump out of the pond, but add my inexpensive bubbler to keep a hole open. The plans for my bubbler came from the link listed below.

Here is a link that might be useful: Mr. Hemenway's bubbler

I run a 2400 gph pump and take the fountain off so the outlet is about 6" below the water surface. It keeps a hole open. I've also used the Walmart air pump, homemade bubbler that works well also.

The problem with 18" is it is above the frost line for your area, so if you get an extended, severe artic deep freeze it might not matter what you are running. The cover would help in that situation as long as the snow could slide off to one side.

Help. I have a small waterfall pond (my very first landscaping project) and I need some advice on how to winterize it. I buried the pump cord under the stones (w/out thinking about how I was going to bring it inside for the winter- I assume I am to bring it in???) and dirt and I cannot get it out w/out tearing the waterfall apart. I drained (not sure if I should have drained it completely- will it crack?) the pond and unplugged the pump yesterday to clean it, but I am not sure if this is what should be done. Can the pump remain outdoors all winter long getting snow covered? Should I cover it up (pond/pump)? I do not have any fish in the pond. Any help you can provide would be wonderful

kennysue: Water will always expand when it freezes, and it is very strong. If there is any water in your pump chances are it will break when it drops below freezing.

Last winter I had a 2 foot diameter plastic pond break when the little water in it frooze. It just broke out the bottom

However... if you leave it running as long as it is getting water continiously thru it then it probably will not freeze. The slightly warmer water in a pond naturally sinks to the bottom, colder water rises where it freezes. That's why a lake freezes from the top towards the bottom and doesn't freeze solid. So if your pump draws from the bottom and the pond doesn't freeze solid you may be OK.

Unless you heat under a cover (small lightbulb?) then a cover isn't going to keep out the cold.