Just saw this note (sorry bout that) been out cutting cattails all day,Im not concerned about having an opening as much as I am about some clear ice, 30 minutes per day will probably be too much with your aeration system. As long as you have 25% clear ice let it freeze over, The idea is to pump some water like you have on top of the ice to melt off the snow and then use the ice as insulation.
If you open up the ice cover every few weeks you wont have to worry about gas buildup and may not have a problem even without an opening in the ice, I don't think you have a lot of plant material at present that would consume DO in dark water.
My lower pond has been covered for two weeks now and is still at 90% saturation and has a higher BOD than yours so you should be in better shape.
Last edited by Bill Cody; 01/19/20 05:44 PM.
