Good job Wayne! Nice to have open hole. My cattle heater has the element exposed, and I keep it where the water moves fast, that way the fish don't "hang out" at the heater. Watch to make sure fish are not "hanging out" around heater as the "hot and cold" temperatures can make fish sick. If you see fish around the heater, move the heater close to the bubbler, where it should be.
Mitch, about that foam insulation, I would not recommend covering pond at all, not natural and can cause mold and fungus to grow in the pond in the dark. Many years ago I did cover my pond with a home made "green house". The problem with the plastic, was that it filters out the sun's strongest spectrum of light, and mold can grow, as that happened to me, and this is a common problem with plastic greenhouses. Come spring, the mold was everywhere, on the liner, on the fish, and I was horrified. I took the greenhouse cover off and the mold eventually went away naturally as the sun burnt it out. I did also use liquid pond peat, as that is a natural funguicide. I love pond peat, but product was expensive and find that leaves do the same thing, as they decay, and that is why I leave some leaves in the pond over the winter. I think some leaves are actually very good for pond life, and it is natural for ponds and lakes to have leaves, as there is no natural lake or pond without trees, and they have adapted together over millions of years, with all the pond life.
If you cover your pond with foam, there will be no light shining into pond, and after six months in the dark, that can make fish weak, and if you add mold and fungus on top of that, fish can start dying off. If you have ice, the light can reflect through the ice and will keep the mold and fungus at bay. I think that ice ice and snow can also help keep the pond warmer as well. As long as you have open water holes and water moving you should make out fine. I use my heater only as needed, and the bottom pond is mostly covered in ice now with a hole open where the water flows. The top ponds do not ice over as much as the water moves faster there. My goal is to have the ponds 75 or 80 percent covered with ice before I use the heater.