How do we get rid of duckweed and watermeal covering our HOA pond?

By OurHOA · General information · Revised October 30, 2026

How an HOA board controls duckweed and watermeal on a pond: telling them apart, cutting nutrients, skimming, aquatic herbicides, fish kill risk and permits.

Part of the HOA board handbook: vendors, projects and upkeep.

The short answer

Duckweed and watermeal are tiny floating plants that can cover a still pond until it looks like a green lawn. They thrive on still, nutrient-rich water, so the long-term fix is less fertilizer and goose waste reaching the pond and more surface movement. For a mat that is already there, small ponds can be skimmed, and larger ones usually need a licensed aquatic applicator using an herbicide labeled for these plants. Treat early, before the plants cover most of the pond, and treat a heavy mat in sections so the rotting plants do not strip the oxygen from the water and kill the fish. Expect repeat work: Penn State Extension says chemical control often has to be repeated every year or several times a year. Permit and license rules differ in Texas, Florida and Colorado and by your governing documents. This guide is general education, not legal advice.

Confirm what is on the water

Identify the plant first, because the two respond to different treatments. Duckweed. Penn State describes round to oval fronds 2 to 6 millimeters across, each with a root hanging underneath. Clemson's Home and Garden Information Center compares one plant to the size of a pencil eraser. Watermeal. Fronds are 0.2 to 1.5 millimeters and rootless, and Penn State likens them to grass seed floating on the water. Clemson compares one to a pencil tip. The UF/IFAS plant directory lists watermeal as native to Florida and repeats a botanist's field test: rub a handful of the green film between your palms, and watermeal feels gritty, like meal. The two often grow together, and watermeal hides inside duckweed mats. A scoop in a white bucket or a clear jar settles it. Planktonic algae, by contrast, looks like paint or pea soup with no separate plants you can see, and that is a different problem. If you see a scum that looks like spilled paint, read our guide on handling toxic blue-green algae in an HOA pond before anyone touches the water.

Why your pond grows it

Both plants need two things: nutrients and calm water. Penn State names excess phosphorus and nitrogen as the underlying cause and lists the usual sources around a residential pond: lawn runoff, fertilizer spread near the water, septic systems, and ducks and geese. Waterfowl also move the plants from pond to pond. Penn State notes the fronds lodge in their feathers, and Calm water is the other half. Clemson says the plants spread fastest in nutrient-rich water with little airflow, and suggests removing trees along the pond edge to let the wind reach the surface. The cost of ignoring it goes beyond looks. Clemson explains that a heavy mat blocks sunlight from the phytoplankton below and cuts oxygen exchange with the air, and that these plants release their oxygen into the air rather than the water. Less phytoplankton means less food at the base of the chain that feeds the fish. That gives the board a prevention list it controls: - A no-fertilizer strip of taller grass or plants around the bank, written into the landscape contract. - Clippings blown back onto the turf, never into the water. - No feeding of ducks and geese, with signs and a rule. - A fountain or aerator that keeps the surface moving.

Removal and control without chemicals

Skimming. Penn State says netting, raking, or skimming with a pump or vacuum works on small ponds, and it pulls nutrients out with the plants. Pile the removed plants well away from the bank. Penn State warns that wind or runoff can carry dumped material back into the pond. Skimming can keep up on a half-acre pond. On three acres in July, it will not. Surface aeration. Penn State notes that surface-disrupting aerators confine growth to the pond edges, where it is easier to net. A bottom diffuser that only bubbles may not move the surface enough, so ask the vendor which kind the pond needs. Our guide on replacing an HOA pond fountain or aerator covers sizing, power and bids. Grass carp. Penn State says grass carp give some control of duckweed but not watermeal, and they often eat other plants first. Texas requires a Parks and Wildlife permit to stock sterile triploid grass carp, and other states have their own rules, so check before ordering fish. Tilapia. Texas A&M AgriLife's AquaPlant site says Mozambique tilapia eat both plants but die when water drops below 55 degrees, so they need restocking each spring, and a large bass population may eat them first. Texas requires TPWD approval in its conservation zone and a permitted seller everywhere. Elsewhere, ask the state wildlife agency first.

Herbicides and the fish kill problem

AquaPlant rates the aquatic active ingredients against each plant, based on U.S. Army Corps of Engineers trials. For duckweed: carfentrazone, fluridone, flumioxazin and penoxsulam rate excellent, and diquat rates good. For watermeal: flumioxazin rates excellent, and fluridone and penoxsulam rate good. The products work differently. Fluridone is a slow, systemic herbicide applied to the whole water body, and Penn State says it works best in ponds with little or no overflow. A pond that drains through an outlet after every storm can wash it out before it works. Flumioxazin and carfentrazone are fast contact products. AquaPlant says flumioxazin breaks down rapidly when the water's pH is above 8.5 and needs a surfactant on floating plants. Oxygen is the real risk. AquaPlant warns that decaying plants after treatment can deplete oxygen and kill fish, and says to treat heavy growth in sections, wait about two weeks between them, and run aeration, especially at night, for several days afterward. Texas Parks and Wildlife says that when growth covers more than half the pond, treat about a quarter at a time with 10 to 14 days between sections, and avoid spraying on cloudy days, when oxygen depletion is more likely. Two more checks. Every label carries water use restrictions, so if the association irrigates from the pond, ask what treatment means for the sprinklers. And timing matters: Penn State advises treating before the plants cover most of the pond, which means acting when the first patches show along the calm side, not in August.

Permits and licenses in Texas, Florida and Colorado

Texas. TPWD's plant management page says a treatment proposal must be filed with the department and the controlling authority before treating public water, and that none is required for private water. Treatment with a restricted-use or state-limited-use herbicide still requires Texas Department of Agriculture certification. Florida. Section 369.20(7) of the Florida Statutes bars anyone from controlling or removing aquatic plants in waters of the state without a Fish and Wildlife Conservation Commission permit, unless a commission rule exempts the activity or the water. Rule 68F-20.0035 exempts, among others, artificial waters and waters under 160 acres that are not public waterbodies. Those exemptions are lost if herbicides are used while the water connects directly to Waters of Special Concern, or if it connects to a manatee aggregation site. Exempt waters must still follow label rates and the rule's general conditions. Have the applicator confirm which one in writing. Colorado. C.R.S. 35-10-105 requires anyone acting as a commercial applicator to hold a commercial applicator business license from the state agriculture commissioner, so the contractor who treats the pond for hire needs one. If the pond is a detention basin under a city or drainage district agreement, read that agreement before adding anything to the water.

A sample year and wording to copy

A sample year for a Texas or Florida pond. Colorado boards can shift each step later, once the water warms. - February: the operations director and contractor walk the pond, take jar samples and photos from fixed points, and check the aerator. - March to April: watch for the first green specks along the calm side. Treat early, by section if needed, or skim if the patch is small. - May to September: a monthly contractor visit with a written report listing the product, EPA registration number, area treated and photos. Aerator on every night after a treatment. - October: the contractor reports what came back, and the board sets next year's budget line. A motion: 'Move to approve [contractor]'s aquatic vegetation proposal dated [date] for duckweed and watermeal control on [pond name], including treatment in sections as described, at a cost not to exceed $[amount] for the year.' An owner notice: 'The green film on [pond name] is duckweed and watermeal, tiny floating plants that feed on nutrients from lawn runoff and waterfowl. On [date], [contractor], a licensed aquatic applicator, will treat part of the pond with an herbicide labeled for use in water. We are treating in sections to protect the fish, so expect some green to remain for several weeks. You can help: please do not fertilize within [distance] of the water, keep grass clippings out of the pond, and do not feed the ducks or geese. Questions go to [contact].'

Mistakes boards make

The expensive one is waiting until the whole pond is green in August and then treating all of it at once. That is how boards end up paying to haul away dead fish. Next is buying a product that worked on a neighbor's duckweed when the problem is watermeal. Boards also skim the mat and dump it on the bank, where the next rain washes it back in, or pay for one treatment, call the job done, and skip the work that keeps nutrients out. And they let a waterfront owner pour a hardware-store product into the pond, which may break the label, the Florida permit rules, or both. Put pond treatments under one contract, one map and one budget line, and adopt a rule that only the association's contractor treats the water.

Sources

These guides are general education for HOA boards and residents, not legal, tax, or financial advice. Rules vary by state and by your community's governing documents - check with a professional for your situation.

More on living with an hoa

Or browse all living with an hoa guides.