Although you are creating some water circulation, the amount of dissolved oxygen that is being created may be a lot less than you think. With an actual subsurface, forced air, aeration system, you are circulating a much higher volume of water. Some systems circulate over 5,000 gallons of water per minute. I know that Vertex aerators are pretty top notch and operated a very reasonable monthly electrical cost. If you are looking to really circulate that pond and make your fish happy, I would look into a vertex system.

Miles upon miles of aeration line installed, 2500 plus pond treatments performed annually.... and I'm just getting started.