Sadworld, I'm not an expert, but I plan on aerating in 4FT. of water to keep an opening in the pond for the trout. I have a soaker hose coiled in a 10 FT. circle. When it gets really cold I figure on running aeration full time if needed.
Right now I have my aerator set on a thermostat to turn on when the air temps. reach above 55 degrees,this helps to keep the pond a little warmer. I do the opposite in the summer. Just my 2 cents.