Not sure if anyone can help but we have a large pond at our parents house we installed 2 years ago. One end is 3 feet deep and the other 2 feet. First year frozen dead fish come winter!!! So we do some investigation and the local stores tell us to get a heater, as long as there is a hole in the ice there will be room for exchange of gasses. So we buy a heater and when it froze this year all the fish GUESS..............DEAD!!!! The fish are darn expensive and not only that i dont like killing things!!! The local store said, oh you must have had leaves in the bottom and they got hungry and ate the leaves which ate a hole in the stomach lining and killed them. I think its B.S.!! Now i was at a guys house today with a similar pond and his fish have been great for 4 years. All he had was a small bubbler for aeration to oxygenate the water and keep it from freezing!!! Any comments or thoughts?????????