It's not algae; it's a member of the Araceae family, commonly referred to as duckweed.

Visitors to Lithia Park's upper duck pond have been surprised to find it covered in a layer of thick, green ooze. It's not algae; it's a member of the Araceae family, commonly referred to as duckweed. The stemless plant grows in water, spreading as it connects to other duckweed, and reproduces extremely fast.

"We've always had a little bit in the upper duck pond," said Don Todt, lead horticulturist for the Parks and Recreation Department.

Though the plant looks far from appetizing, ducks love to feast on it. In doing so, they help control its growth. But there have been fewer ducks at the pond since the city began discouraging residents from feeding the ducks after health concerns rose over the spread of bacteria.

Without the ducks, Todt said, "The duckweed is able to basically stay in one place, and reproduce until it covers the whole pond."

He added that, unlike the bacteria ducks can leave, duckweed poses no health risks.

But as the empty benches around the pond indicate, it is not much fun to look at. Visiting from Seattle, John Derven took a glance at the pond as he walked by and kept walking.

"No thanks," he said.

At least 100 ducks were in and around the pond in years past, Todt said. This month, there are about a dozen. As a result, trying to rid the pond of excess duckweed has been "an exercise in futility," he said.

That should change as fall approaches. Park staff are preparing to circulate water from the TID ditch throughout the pond, as part of a larger plan to irrigate Lithia Park. That influx should create some much-needed water movement in the pond, Todt said.

"Plus, around the first of September, the ducks will filter back in," he said.

He expects the duck population to go up in the fall, even if people are not feeding them. As the temperature dips and heavier winds pick up, the plant will wash onto the ground and dry out. Still, it has made the upper duck pond a lonely place this summer. Todt said that is a shame.

"If you brush the duckweed aside just a little bit, you'll see the water is perfectly clear," he said. "But I guess people that are used to going to the upper duck pond are used to seeing water, not something that looks like a golf green."