Hi Cheryle...I've been using the air pump exclusively..it keeps a hole in the ice fine. It runs 24/7

Hey, Cheryl. What you use depends on conditions in your area. The important thing to have is an opening in the ice so gases that are formed by decaying organics can escape. It does not need to be huge. Many if not most of us, also use some way to circulate the water and add fresh air/oxygen to the water. I use a Tetra air pump that is for a large aquarium. It is protected from the weather by covering it with an inverted flower pot. The small amount of heat produced by the air pump keeps snow and ice from building up. The pump has two air lines for my 1,000 gallon pond and I run this air pump 24/7 all year. When the pond is totally iced over this pumped air will help keep a hole open all by itself but mainly I see it moving under the ice to the hole that is made by whatever de-icer I am using.
I have had the most success with keeping a hole in the ice with a home made de-icer. It is an inverted Rubbermaid storage box floating on a raft of blue board foam insulation. The raft of course has a hole in it that exposes the inside of the box where there are two 60 watt lightbulbs burning. I found out that I could probably go with a smaller box and only one lightbulb and have it work just as well. The raft keeps splashing to a minimum so the bulb doesn't break so long as the blue board is at least 4 inches wide all around. When the pond is frozen over the raft becomes frozen in place but the surface under the box is ice free. The heat is apparent because the top of the box is free of ice and snow. I have often seen cats and squirrels napping on top of it. There are other designs shown in the fax section of this forum. Do a search.
I bought a new and different commercial de-icer made by Tetra this year but I have not used it yet. The waterfall and the pump that feeds it have continued to run despite the temperatures. At times the hole has become quite small but it has not yet closed up entirely. Right now the entire surface is ice free.
I know this is unusual and eventually I will need to use some sort of de-icer but I am going to let it run as long as possible since the water is being filtered as long as the pump is sending water to the Skippy that forms the waterfall.
If you continue to use your pump to circulate the water you should consider running a length of 1/4 inch tubing to the outlet connector to pull in fresh air. There are connectors that already have a nipple to add on the 1/4 inch air line. You just have to make sure the end of the tube is not blocked by ice or debris so it can pull air.
As I said, what you do depends entirely on conditions in your area. Sandy

There are two methods used to keep an opening in a frozen pond surface. One is to heat the water. The donut deicers and stock tank heaters use heat and are generally the most expensive method. Deicers generally use about 100 watts of electricity and the stock tank heaters use 1000 to 1500 watts.

Another method is movement. Water that is moving requires colder temperatures to freeze. Pumps and air pumps add movement to water. Smaller pumps will use about 40 watts while an aquarium air pump runs on about 4 watts.

An aquarium air pump is the most economic method and also helps fish by adding oxygen to the water. The bubbles will help bring any toxic gases to the surface as well.

In zone 5 an aquarium air pump may fail to maintain a hole during extremely cold weather. A backup method is a good idea.