We understand your wanting something different than netting or overhead wires, but these are by far the best options. For a small pond, you could try a dog on a leash or run. You can also try increasing the pond's depth so the birds can't stand in it. Fishing line or netting resting in the water and out of sight, may provide the protection you desire while resolving the aesthetics issue. Bird predation at fish hatcheries.

If the aforementioned suggestions are not viable, you can explore other options employed at commercial fish-raising enterprises by visiting Bird damage at aquaculture facilities.

You may find that some frightening techniques might work in your situation. Bird Dispersal Techniques.

Finally, there is a mountain of information at our Digital Commons. A literature search can be done on over 3,200 documents (and growing) WDM Digital Commons. Additional articles from the Vertebrate Pest Conference Proceedings can be obtained at VPC Proceedings. Just click for the tables of contents to see if there is a relevant article.