What the Pond Expert Saw

Field note 260831 · August 31, 2026

At the end of August, I walked a pond specialist from OSU Extension around our pond with a list of worries. By the time he left, most of them had shrunk, and a couple of new ones had moved in.

Good signs first

The pond is full of newts and dragonflies, and he took both as good news: signs of a reasonably healthy pond. He didn't see strong signs of stress.

He also straightened me out on something I'd had wrong. Blue-green algae being present is not the same as it producing toxins. Toxins take particular conditions, often linked to a stressed pond.

I had the plants wrong, too

I'd walked him around naming plants with some confidence. His follow-up email corrected most of my list:

• The tiny floating green on the surface is mostly watermeal. Duckweed grows at the spring.

• The stiff submerged plant I'd been calling milfoil is more likely coontail, a native.

• The pondweed is probably a native species, not the invasive curly pondweed.

Both watermeal and duckweed are high in protein. Harvested, they can go to the chickens, who may find themselves with a new item on the menu.

The pond is slowly becoming a marsh

Our pond is slowly filling in, headed toward wetland. Keeping open water means managing it, but gently. His advice was to remove vegetation in stages, about a third at a time, so the pond's balance isn't upset all at once. Compost what you pull out downstream of the pond, so the nutrients don't wash right back in.

For the muck on the bottom, he suggested aeration: a pump on shore feeding several bubblers on the bottom. Extra oxygen helps the muck break down. He added that bubblers alone don't mix the water much, so a full setup pairs aeration with a circulator.

The dam deserves attention

This was the part I hadn't thought enough about, and it's the part that matters most if something goes wrong:

• No woody plants on the dam. Roots, living or dead, can open channels that let water work through the berm. A falling tree can pull out a chunk of it.

• Watch the cattails. They can work into a dam, too. Ours stay near the water's edge, and mowing keeps them in check.

• Plan for a blocked outlet. Our outlet pipe is about 14 inches across. In roughly 20 years, water has reached the top of the dam only once, when beavers plugged the outlet. That's a story for another post. A protected emergency spillway would give water a safe way out the next time.

Testing before guessing

I want to know whether nutrients are feeding all that floating growth, and where they come from. If testing has to be limited, he said to start with three spots: the creek inlet, the runoff below our chicken coop, and the middle of the pond. Start with nitrate, total nitrogen, phosphate, and pH. He pointed me to the state's list of accredited labs.

A few other answers

• Dying alders on the bank aren't a big concern. Alders are short-lived. A fallen one could even go in the pond as habitat, and a basking log for the newts.

• Barley straw targets true algae. It isn't expected to stop blue-green algae.

• Dredging is expensive. Before any digging, permits and water rights need checking first.

I came away with less to worry about, a better list of things to do, and a new respect for newts.