new pond new frogs new problems

[snowshoes]

5 years ago I moved into home that had a small filthy pond but with health plants fish and frogs. Last winters cold killed off the frogs. The pond was 3 feet deep with an inch of sludge on liner. My new pond is large and almost 5 ft deep.What should I do to help my 3 new green frog survive the winter? I am located in Southern Ontario
Thanks