Just an observation about the dye used in the pond.....You said you thought it would keep temps down, but I believe it did just the opposite and raised the water temperature. Darker colors absorb sunlight and heat, lighter colors will reflect more heat. Also placing your new diffusers only 4 feet from the surface will leave most water under them un-mixed and oxygen will be quickly depleted and even possibly stratify the pond.
Just some quick thoughts.....
