If there are raccoons in your area, you really want netting over the pond.
The standard advice for preventing fish loss to raccoons without using netting is: the water must be at least three feet deep (any less than that, and the raccoons will hang from the edge by their hind legs and grab sleeping fish off the bottom) and you MUST NOT train your fish to surface near the edge of the pond (fish have trouble distinguishing the sound of human footsteps from the sound of raccoon footsteps). Any food should be thrown into the pond at least three feet away from the pond edge.
Naturally, that advice isn't very helpful for a pond six feet or less in diameter.
The standard advice for preventing fish loss to raccoons without using netting is: the water must be at least three feet deep (any less than that, and the raccoons will hang from the edge by their hind legs and grab sleeping fish off the bottom) and you MUST NOT train your fish to surface near the edge of the pond (fish have trouble distinguishing the sound of human footsteps from the sound of raccoon footsteps). Any food should be thrown into the pond at least three feet away from the pond edge.
Naturally, that advice isn't very helpful for a pond six feet or less in diameter.