I have had a few questions about ponds freezing solid. What to do with the goldfish?
You have to catch them and bring them inside. I have heard that goldfish can freeze and survive, but have never seen it happen, so bringing them in is best. But first, how to catch them?
1)Fill a container with pond water.
2)Get a bucket of very warm, even hot, water.
3)Pour it slowly into the pond. The fish will come toward the warm water.
4)Use a net, catch the fish and put them in the container full of pond water. Water is heavy so don't make the fish container too big or you won't be able to carry it.
5)Let the fish warm slowly in that same pond water before you transfer them to their winter home.
By the way, if the pond does ice over, do NOT hit it with a hammer to open a hole. The blow could kill the fish. One way to open a hole is to put a pan of hot water on top of the ice and let it melt.