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I tried that last year with a heater and it still froze solid.
if you live lake front find a junk clothes washer that has a stainless drum in it. take it out and put it in the lake maybe put in a bubbler to keep it from freezing.ive been selling these drums to guys that live on lakes for livewells for fish and bait.they are nice and big with little holes already in them and stainless wont rust away.ive got one in my pond that I keep my catfish bait in and the fish will last forever without water changes and food gets in the drum naturally too.i didn't use a top on mine but when its really sunny out it reflects off the stainless steel and stresses the fish a little but i installed a top and it works great.