Found this - I guess they're not much of a fish eater...

"What do mallards eat?
Mallards are dabbling ducks, meaning that they do not dive underwater for their food, but feed at or just below the surface. They are well adapted to eating both natural and Âdomestic foods (such as waste grain from harvests). Most of their diet is made up of plants, such as wetland plants and grains (like wheat, barley, rice and oats).

On occasion, mallards will eat animal foods. In coastal areas, mallards have been known to eat mussels. Mallards in other areas have also been observed eating insects and other invertebrates.

Each spring, the female mallardÂs diet switches from plants to aquatic invertebrates found in wetlands. This diet provides her with the nutrition and energy she needs to lay and incubate a clutch of eggs.

During the lead-up to the fall migration, mallards tend to take in more food. By building up a store of fat on their bodies, they have a ready supply of energy and are better able to survive the cooler temperatures and long migratory flights."

Sounds like the fish will be ok, though I guess a tiny fry could be mistaken for ?????????

S

you will have two problems with wild ducks visiting your pond.

First.....they will foul (sorry for that pun) the water beyond what your filtration is designed to handle.

secondly and most dangerous....they can and will bring parasites to your fish from the wild water habatits they visit. I would strongly discourage them from visiting.

and thirdly....if you have potted plants they will destroy them. I had a pair of ducks in my pond and every pot was tipped or dug out and the plants floating. I am setting up a blind on the patio! :)

Valid point about the parisites. Bummer...
6:30 this morning the two of them were swimming around in the pond and a school of fish (Comets, Shubunkins, Gold) seem to be following them around. Enjoyable to watch since the ducks were ignoring the fish and seemed more interested in the remaining string algea.

My wife and I have spent considerable time and money for the birds with multiple feeding stations, breeder houses, selecting trees and plants for bird habitat, etc. Hard to inforce a "by invitation only" policy.

From what I've read, as soon as the male actually mates with the female and she lays eggs, the male will leave. That may solve the problem on it's own.

Here is a link that might be useful: (Mallard ducks)

Valid point about the parisites. Bummer...
6:30 this morning the two of them were swimming around in the pond and a school of fish (Comets, Shubunkins, Gold) seem to be following them around. Enjoyable to watch since the ducks were ignoring the fish and seemed more interested in the remaining string algea.

My wife and I have spent considerable time and money for the birds with multiple feeding stations, breeder houses, selecting trees and plants for bird habitat, etc. Hard to inforce a "by invitation only" policy.

From what I've read, as soon as the male actually mates with the female and she lays eggs, the male will leave. That may solve the problem on it's own.

Here is a link that might be useful: (Mallard ducks)

they won't stay long. no problem. just don't allow any geese.