Besides scaring my cat, is there any harm that happen to the pond - they don't eat fish do they??? I hope they don't poop into the water because there's already enough organic debris and fish poop to keep up with.

I am not too concerned about the poop because the pond is large but with your size it may cause a algae bloom.

Other animals are attracted to their nests. Duck eggs are great food for many common predators. They destroy the rest of the eggs for the heck of it. I have cleaned up scattered baby duck body parts once too often. The parents are trying to nest in a very unsafe place. They need other ducks around them to better the odds of the duckling's survival.

Ducks are not good for your pond and your pond is not good for the ducks.

Eggs and common predators? Predators! oh you betcha; just add bacon and breakfast is served, yum.

I'm not certain how to handle this situation being as they are good neighbors (other than wanting me to coop up my ducks but they are unwilling to coop up their cats who get into my trash). I'm half tempted to ship my beautiful Rouens to someone else's pond to live and then wait for duck season to pop the wild drake. I hate the idea of having no ducks on my pond, but how on earth do you keep them home while preventing wild ones from dropping in? I am pretty certain Texas Parks and Wildlife is going to tell me that I created "habitat" when we built the pond, and that we now need to allow the wild duck to live there. I dare say they won't feel the need to utilize public dollars to try to capture a wild drake whose only real crime is stealing cat food and pooping on the neighbor's porch when they are trying to sell the house.

I'm having such problems, and I have no idea how the OP would go about getting wild ducks to leave a pond. I would love suggestions on how to get my wild mallard to leave for good. He flies all over the neighborhood each evening, but is always back by morning.
Cheers
M