I don't know why it wouldn't do the same job in a big pond that it did in the small one. A hole is all you need.

Thank you. That's what I was thinking.

Agreed! A hole is a hole is a hole, no matter how much water is under it!

We use an aquarium bubbler -- placed inside a peanut butter jar,
hung upside down with a hole in the lid for the tubing to exit.
The jar is placed on a stick about two feet above ground to keep it away from
the snow.

It works great all winter keeping a hole in the ice.
it's inexpensive to buy and inexpensive to run.

An aquarium bubbler is a good choice. There is a potential problem with the power cord, which is not rated for outdoor use or wet environments. Use a larger plastic container to protect the bubbler from the weather. The power cord should be protected inside of the container and an outdoor rated extension cord should be used outside of the container.