I will reserve comments until the O2 and temp readings come in. I'd love to see the temp profile for the pond from just below the ice to the bottom in the deepest part of the pond, then correlate that to the depth that the diffusers are placed at. I'd love to see you do something next year, but I'll not say what it is until the temp profiles come back.
I'm going to check on a system that was installed to keep ice from forming around a pier, and I will report back once I see how it's going this year.
I got to admit, I'd love to hear your theory now instead of after the results come in!!
I have said this before, but I will say it again. I will 99.9% guarantee the water is basically homogenous. It has been over the past 2-3 winters when we were pumping far less air so I've got to imagine this year the water will be even more fully mixed. In past years we had less than half a degree of difference in temp from top to bottom. I believe I am achieving this in winter due to cold waters ability to move easier and farther than warm water. IIRC Bill Cody has stated that in winter he has documented a diffuser moving water 200' away due to cold water moving easier than warm water. Jeff in MN has a Youtube video of GoPro footage filmed under the ice of a single diffuser moving water even further away than that.
I just do not see how the pipe is not a homerun at this point. There's no question DO will improve with a hole open and there seems to be no question that a pipe in the plume either causes the hole to reopen MUCH faster OR keeps a hole open that would otherwise be iced over solid. That HAS to be a win for DO levels and water quality.
I am starting to believe plume intensity matters much less than I thought, at least in my setting. If plume intensity mattered I do not see how the koenders could currently have a hole open and the close dual is frozen over solid. The koenders has about the weakest plume you can imagine and the close dual has a downright ferocious plume. What is happening right now makes no sense to me if plume intensity actually matters. I am also not convinced the coarser bubbles would help my ice doming situation. If the ice domes up and is no longer touching the surface of the water how would coarser bubbles help at all? That is why I am sticking with the vertex diffusers. The pipe opens the hole and then the vertex fine bubbles moves more water to the surface for gas exchange than the coarse bubbles would.
Honestly I just don't think we can compare systems in your area to these true "northern" systems. You guys might get an inch or two or three, right? I am getting three feet of ice!!! IMHO, Jeff in MN is the closest comparison to what I deal with. He gets MUCH colder temps than I get, same amount of ice, less snow than I get and then I have altitude always working against me. I think the amount of ice we get, the rate at which the ice can form once aeration turns off, how low the water temps get, how long our water is under ice, etc are game changers for us and require solutions that you guys never have to worry about. I think there is a reason you have never had to deal with the ice doming up, yet Jeff and I both have dealt with it every single year. Jeff has disproven a LOT of winter aeration stuff that gets regularly posted and reposted here on PB, but he won't post any of his findings because he just doesn't care to argue it with folks. For instance, he now runs his aeration 24/7 all through the winter. He "super chills" his entire pond down to 33 degrees or less. In the spring at ice off his LMB are coming out fat, happy and healthy with impressive growth over the LONG winter under thick ice. That isn't supposed to be possible, right? Yet it's happening.
Bill Cody has said this quite a while back and I agree more now than ever. I think we have a LONG way to go to fully understand aeration under the ice, especially thick ice.