Heron are smart. We have heron and egrits in our neighborhood, and they will return to where they find food.
When my son was young, he would feed an egrit that would come to our yard everyday at the same time. The bird was sooo tame, he would walk right into our house.
Don't put any fish back in the pond for awhile. The heron will come looking and when he gets the idea there's no food there, he'll move on and find another feeding ground.
When you do put fish back in the pond, try a couple strands of monofilament strung across the pond.