Algae and Aquatic Weed Control
Duckweed vs Watermeal: How to Tell Them Apart & Remove Them
Aug
Last Updated on August 12, 2026 by Adam McBeth
Watermeal is often mistaken for Duckweed, but watermeal is smaller in size.
| Duckweed | Watermeal | |
|---|---|---|
| Size | Oval, ~1/8 inch, visible individually | Grain-sized, almost dust-like until it mats together |
| Shape | Tiny leaf-like fronds | Round, rootless |
| Physical removal | Rake off the surface | Needs a fine net – too small to rake |
| Spreads via | Wind, wildlife, water flow | Same, but harder to fully clear once established |
| Commercial system | Both duckweed and watermeal are free-floating and need still water to establish. A surface aerator or floating fountain keeps the surface in constant motion, preventing new colonies from taking hold and helping push existing growth toward shore for easier removal. | |
Helpful Duckweed and Watermeal Control Tips
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Circulate the water
Duckweed and watermeal are invasive pond weeds that thrive in plant nutrient rich water. Aeration will help deplete their food supply.
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Add safe chemicals
Fluridone, Flumioxazin, and Penoxsulam are chemicals that can treat both duckweed and watermeal. We always advise extreme caution when pursuing a chemical remedy for pond maintenance issues.
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Use a lake rake
This method works for duckweed in particular, as watermeal is extremely difficult to physically control. Rake duckweed to the edge of your pond and remove it.
Understand the building blocks to keeping your pond in its healthiest state, naturally.
Watermeal
Watermeal is a tiny rootless floating plant. It is hard to see until it groups together, in large colonies on the surface of the pond.
Watermeal is a native weed, and is also invasive. Duckweed and mosquito fern often grow along with watermeal. Like all other floating weeds, if it is allowed to spread and cover the surface of the pond or lake, it will deplete the oxygen and possibly cause fish kills.
Watermeal is not a food source for ducks, but ducks will often eat it. However the ducks can also carry it to other ponds or lakes in the area.
So what are safe control options?
The best way to get watermeal out of the pond is to use a large net with a long pole that has a float on it to scoop it out. It is hard to rake it out because watermeal is so tiny, which makes it so difficult to remove. The Lake Rake is the best option because it has the float on it. That makes it easier to skim across the surface. To make it work better, wrap the Lake Rake with a dense netting, so that it works like a scoop.
The best option is to install a floating pond fountain or decorative aerator in your pond. Both will aerate to put oxygen back in the pond but also, push the watermeal towards the shore for easier scoop up with a net.
Duckweed in Ponds
Duckweed grows in dense colonies in still water, undisturbed by water movement. Usually there is more than one species of duckweed inhabiting a body of water. Duckweed is somewhat oval shaped and is sometimes mistaken as algae.
Duckweed normally is an aggressive pond weed and are often found mixed in with other unwanted weeds. If large amounts of duckweed cover the surface of the pond, then oxygen is depleted and fish kills will most likely occur.
Therefore it is extremely important to get control before they completely cover the surface of the pond.
Submerged parts of all aquatic plants offer habitats for several species of invertebrates. These invertebrates are then used as food by fish and other wildlife species (e.g. amphibians, reptiles, ducks, etc.).
When duckweed dies off, their decomposition of bacterium and fungi provides food for several aquatic invertebrates.
Duckweed
How to Control Duckweed
Ducks will eat duckweed but they are not a consistent method for controlling it. One method reasonably effective method pond owners use to control duckweed is by using a lake rake to rake it off the pond’s surface.
Since duckweed prefers a stagnant water environment, adding a pond aerator puts oxygen back in the pond and will get rid of Duckweed and prevent it from coming back.
If you are having trouble identifying the weeds in your pond, here’s Texas A&M’s AquaPlant identification tool!
Still fighting duckweed or watermeal after raking? Standing water is exactly what both need to keep coming back. If you’re not sure whether an aerator or a fountain is the right fit for your pond, our guide to choosing the right pump, fountain, or aerator walks through exactly how to size the system that’ll keep your water moving year-round.
