If you don't mind me saying, this is a subject that I have quite a bit of experience in.

First of all, pond water receives virtually NO oxygen from bubbles coming from an aerator. Pond water DOES receive oxygen from photosynthetic plant activity and also from atmospheric oxygen exchange at the pond's surface. In other words, the greater the surface area at which water meets air, the more oxygen diffuses into the water. An aerator facilitates this process by allowing more water to meet the atmosphere by surface agitation. Well water, although anoxic as it comes from the ground, can quickly be oxygenated by mixing or agitating as it meet the water. You can buy yourself a two-dollar sweeper nozzle at Home Depot and spray 4 gpm directly at three concrete blocks placed in series at the pond's edge. We've tested this water and it is already at 5ppm by the time it hits the pond. All six of my ponds are filled with well water and I've never had a DO problem.

This process is helpful in intensive fish culture, and may make you feel better about your pond, but in reality you can go ahead and add your well water and you will almost immediately have algae (and wind action) which will provide adequate oxygenation.

Holding a redear sunfish is like running with scissors.