I bought my ducks understanding the risk to my ornamental pond. But, to be fair, every Spring I have wild mallards free loading from my ornamental pond anyway, so my thinking was, if I have my own ducks, at least I have
some say over when and how often they get to use it
Haven't seen my ducks pushing rocks and dirt in the pond
I do know it looks more murky since they have been given permission to play in it, but, with all their splashing about, it does disturb the silt which builds up in the bottom of the pond naturally. Hasn't deterred the plethora of frogs/toads which are filling the pond with their babies though!
Couple of suggestions:
~ if you want to keep your ducks out, fence them off in their own secure area (prettier than fencing off your actual pond)
~ if the clogged filter is the primary issue, would a stronger filtration pump work?
I think there is a compromise to be found which will please your ducks and dh. You just have to work with understanding the needs of your ducks vs the needs of your pond. In my case, because I love seeing my Khaki's *in* the pond, they are given access first thing in the morning and once again during late afternoon/evening. The rest of the time they are kept to their own part of the garden and have a tub of water for their needs.
What breed of ducks do you have? How many? What size is their own pen? How many hours are they free ranging in your garden/accessing the pond? Knowing the answer to these questions would help people in the advice they offer you.
Good luck!