Have been aerating my pond over the past two years with a 200L/m air pump.

The pond is at most 4m deep at the deepest point with an average of around 2m (6 feet) over most of the bottom.

The aerator is set at around 3m or around 9 feet. My question to you is that an air pump such as this is turning over a lot of water and pretty much stopping a thermocline. However, ive been looking at airblowers which put out around 2000L/m. To increase air going into that column if air/water coming up from the bottom of the pond is it better to put an aerator that is punching out an additional 2000L/m into that column at around 1-1.5m below the surface of the water?

Interesting through?

What kind of diffusers are you using? Do you have a plate under them? Have you measured the water temps top to bottom in the deepest section?

I've read that a lot of air volume isnt necessarily what you want. The volume should be regulated to the type of diffuser to get you as many tiny bubbles as you can. If your over powering the membranes your basically throwing money away.

Mike is correct always remember that you want your diffusers to have as small of bubbles as possible. The smaller and more you have the better uplift you will get from them verses big round bubbles. The uplift to the surface of the pond is what you want. As that bottom water hits the surface of the pond it will grab oxygen and then do it all over again as it pushes up and out. This will eventually create your turnover in your pond.