AZ, I think we can relate to each other in that I am in Minnesota where things freeze over pretty good. Based on what I know you are on the right track. I consulted some experts when I built my 1/2 acre pond (100 x 400 feet)and immediately determined that I need winter aeration to avoid winter kill. You need to be careful with winter aeration in our cold climates though since if you cool the water too much I've been told the fish will be unable to aspirate oxygen and will die even if there is plenty of it. I've been told this occurs if the bulk of the water gets down to 39 deg. F. So the answer in my case was that before I put fish in my pond I aerated the pond for the previous winter. I experimented with how much time per day I could aerate and not get all the water that cold. I also use a vane pump, 1/2 HP that pumps about 5 to 6 CFM I think. I determined that when really cold I cannot run this for more than 8 hours per day without taking too much heat out. So I run the air pump for 4 hours starting at noon and then for 4 hours starting at midnight. Now since you also want to get as much O2 in the pond during that time as possible I would not use a diaphram diffuser, I would use some good air stones. I bought some stones from Aquatic Ecosystems. They have data in their catalog that can help you calculate BOD and compare what you need to how much your pump and diffuser will put into the pond. I must say that once I determined my pump running time and calculated how many air stones to hook into the system I have run the thing through 3 winters already with not so much as one dead fish evident in the spring or summer. I run the same aerator schedule all year. My pond is very heavily stocked with 1000 HBG and some bass. I also made the mistake of putting a few crappie into the pond and now have many hundreds if not thousands of them. My bluegill and larger crappie are 3/4 pound this year and very healthy. Also note that I put my diffusers on the bottom of my pond in deepest water (8 ft) to keep things from stratifying. I think this gives the fish more livable space. Hope things work for you. Hopefully some of the real experts on this forum will chime in and let you know if I've given an bad advice.

Gotta get back to fishin!