I agree that the farther south one goes the more the aerator has to run to overcome the additional surface heating of the pond. Run times are also dependent on: 1. how big the pond is, 2. tempeature difference between the top and bottom 3. how many acres of water per diffuser, 4. how big the diffuser is and 5. how much air each diffuser is getting. All these things (plus a few more) affect how much and how fast water can be mixed.
