Along with what size is your pond, what is the depth, shape and how does it recharge to maintain the water level?
A 1/3hp piston compressor would have no problem pushing air only 1200' to your pond. A simple 3/4" PVC pipe would work fine. The electrical savings running this smaller pump vs. a 4hp compressor would out weigh the initial cost of the piston compressor, (only $20-$30 per mo. depending on your cost per kw hr.).
As Ted said, very good question. There is someone reading this that wanted to know the answer to this question.
