A circulator and surface aerator fountain with the same size motor are designed to perform different tasks or methods of moving water. Watch the two styles operate and read about the benefits of each style. Try you tube for videos.
Thermal stratification is a feature of water and characteristic of water bodies and not necessarily a bad thing. Deep trout lakes stratify so can shallow ponds. Results of thermal stratification is dependent on the water quality in each pond/lake when and if it can cause problems. As a general rule the cloudier the water the more thermal stratification becomes a concern and more likely a fish kill could occur.
