Duckweed is eaten by a wide range of animals, from dabbling ducks and fish to insects, mammals, and even humans. These tiny floating plants, among the smallest flowering plants on Earth, pack 20 to 46% protein by dry weight, making them a surprisingly nutrient-dense food source across freshwater ecosystems and, increasingly, in agriculture.
Ducks and Other Waterfowl
The name says it all. Duckweed is a staple for many species of dabbling ducks. Blue-winged teal are omnivores whose plant diet includes the vegetative parts of duckweed alongside coontail, muskgrass, and pondweeds. Gadwall ducklings get roughly 90% of their food volume from plants, with duckweed among the key species consumed. Redhead ducklings shift toward duckweed and pondweeds as they mature, moving from insect-rich shallow areas to more open water where floating plants dominate.
Wood ducks, mallards, and northern pintails also feed on duckweed when it’s available. For waterfowl generally, duckweed serves as both a direct food source and a habitat that concentrates the insects and invertebrates ducklings need during their first weeks of life.
Fish That Feed on Duckweed
Tilapia are the most effective fish consumers of duckweed. In feeding trials at the University of Florida, blue tilapia ate an average of 117% of their own body weight in fresh duckweed every 48 hours, with some individuals consuming up to 200% of their body weight in that period. Individually, small tilapia (averaging about 7 grams) ate 5 to 12 grams of duckweed per fish over two days. When stocked at roughly 1,000 fish per hectare in a South Carolina pond, blue tilapia controlled watermeal (a close relative of duckweed) within three months.
Grass carp, often used for aquatic weed control, are far less effective against duckweed. Standard stocking rates of 7 to 15 grass carp per surface acre work well for submerged vegetation but don’t reliably reduce duckweed coverage. Texas A&M’s fisheries extension recommends tilapia specifically for duckweed and watermeal control, at stocking rates of 15 to 20 pounds of adult Mozambique tilapia per surface acre. Koi and goldfish will also nibble on duckweed in ponds, though they rarely consume enough to keep it in check.
Insects and Invertebrates
Several insects feed on duckweed, but the most well-studied is the duckweed weevil. These tiny beetles chew through the fronds and can devastate duckweed mats when populations build up during warm months. A closely related weevil, Stenopelmus rufinasus, has been extensively studied as a biological control agent for water fern (a floating plant often found alongside duckweed). That weevil achieved complete control of its target plant at 81% of release sites, typically within about seven months. The principle is the same with duckweed-feeding insects: small, specialized herbivores can suppress floating plant populations remarkably fast when conditions favor their reproduction.
Beyond weevils, certain moth larvae, aphids, and midge larvae also feed on duckweed. Freshwater snails graze on the roots and fronds, and various zooplankton species consume the microscopic fragments that break off as duckweed colonies grow and decay.
Turtles and Aquatic Mammals
Many freshwater turtles eat duckweed as part of a mixed diet. Painted turtles, red-eared sliders, and snapping turtles all consume floating plants, with younger turtles tending to eat more plant material as they grow. Muskrats forage on duckweed along with cattails, sedges, and other aquatic vegetation. They’re commonly photographed covered in duckweed after surfacing from feeding dives. Beavers and nutria will also eat duckweed opportunistically, though it’s a small part of their overall diet compared to woody plants and grasses.
Why Duckweed Is So Nutritious
The reason so many animals eat duckweed comes down to its exceptional nutritional profile. Protein content ranges from 20 to 30% of dry weight in wild-harvested plants, and commercially grown duckweed can reach 43 to 46% protein. That puts it in the same league as soybeans. The protein quality is high too: duckweed contains all essential amino acids, and its protein digestibility score (89%) is nearly identical to soy protein isolate (90%).
Duckweed is also rich in omega-3 fatty acids, particularly alpha-linolenic acid, and contains unusually high levels of vitamin K compared to other leafy greens. It provides meaningful amounts of iron and folate. These qualities explain why it has been eaten by humans in Southeast Asia for generations, particularly Wolffia globosa and Wolffia arrhiza, which are consumed as vegetables in Thailand, Laos, and Myanmar. The European Food Safety Authority has assessed both species and raised no safety objections for human consumption.
Duckweed as Livestock Feed
The same nutritional density that attracts wildlife makes duckweed increasingly attractive as animal feed. For broiler chickens, duckweed protein contains all essential amino acids in sufficient quantities for growth and performance. Its essential amino acid index for broilers (1.4) is actually higher than that of soybean meal (1.3) or fishmeal (1.2), meaning its amino acid balance is superior to these conventional feed ingredients.
For pigs, duckweed works well as a supplement but has some limitations. Methionine is the most limiting amino acid, particularly for pregnant sows, and histidine can also fall short for growing pigs. Cattle face similar constraints, though rumen bacteria produce much of the protein cattle need, making the amino acid gaps less significant in practice. The main challenge for pigs and poultry is duckweed’s relatively high ash and fiber content, which limits how much can be mixed into feed. Still, its crude protein concentration makes it a promising partial replacement for soy or fishmeal in balanced rations.
Controlling Duckweed Through Grazing
If you’re dealing with unwanted duckweed in a pond, the most practical biological option is tilapia. Their consumption rates are extraordinary for their size, and they target duckweed preferentially. The limitation is that tilapia are tropical fish and die when water temperatures drop below about 50°F (10°C), so they only provide seasonal control in temperate climates. You’d need to restock each spring.
Domestic ducks are another option for small ponds. A flock of six to eight ducks can keep duckweed in check on a quarter-acre pond, though they also add nutrients to the water through their droppings, which can fuel more duckweed growth. For larger bodies of water, a combination of tilapia and aeration to reduce nutrient loading tends to be the most effective approach. Grass carp, despite their reputation as aquatic vegetation control, are not a reliable solution for floating plants like duckweed.