In a neighbors 1/4 acre pond, a single pair kept the water muddy with their constant dabbling around the pond edge. Once the coyotes removed them, the water cleared up.

As for cows/pigs/ducks sealing a leaky pond, I would not stake my reputation on having that happen frequently enough to consider it to be a reliable way to seal a pond. I'd rather place my money on a sheepsfoot roller and clay.........

Depending on the amount of ducks in the pond, if you were going to use the water for fertilizing/watering purposes, and using the ducks for egg production, then I don't think having them in the pond would be bad. But having them in the pond, and either using the pond to swim in, or eating the fish out of it? I wouldn't. But that's just me.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).