The resulting high levels of waterfowl poop are ultimately jeopardizing the water and a fish hatchery downstream.
Meanwhile, the ducks and geese of DeCoursey Pond have developed a taste for the refined things in life - refined sugar, refined flour, refined carbs.
Local resident Havilah Mann always thought she was helping the ducks - fattening them up for the lean winter months.
"They're so cute," she says. "I grew up feeding ducks. My parents do it. ... Why don't they want people to feed the ducks?"
But as volunteers are now explaining to park visitors, all of this "refinement" is actually polluting the birds' bodies.
"Oh my goodness, I thought it was good for them," says Mann.
Says one volunteer, "This kind of processed food isn't good for them. They can't even fly any more, they're so fat."
The problem is caused by junk food. Too many people are feeding the ducks and geese junk food, and they become addicted.
"People come with whole grocery bags from the thrift store, then they feed them chips, leftover Cocoa Puffs - all this white sugary stuff
which causes the ducks to poop more than they need to," says volunteer Clarice Clark.
All that junk food is ultimately clogging Puyallup's Decoursey Pond with poop - it's literally overflowing with bacteria.
"It's causing problems. There's a fish hatchery downstream - they've complained that the levels of fecal coliform are too high, endangering the fish," says Clark.
Now volunteers are trying to save the ducks from their own taste buds - they're building barriers around the waterfront.
"Keeps the ducks in the water," says volunteer Darren Chromey. "Teaches the humans hopefully not to feed the animals."
They're also building relationships with well-meaning people, and teaching them this problem is bigger than fat ducks on a dirty pond in one small town.
"I never thought of the salt, of what's in the bread, about what's good for them," says Mann.
"We all live downstream," observes Clark. "There's somebody upstream of you, probably doing something you wish they weren't doing."