Darrell you ask a very good question. It is a new product so I sure don't know the answer. I can tell you that fish sense low DO levels and move to the best place (high DO) when they need to. In a 4 acre lake I believe all the fish (ok maybe not all but a very high %) would move to the best place. What I don't know is where that would be with this product given the way it works (forcing surface water down).