This duckweed is grown in my greenhouse environment during the summer months you will receive a small plastic tub full, there are many uses for duckweed: Duckweed can purify and concentrate nutrients from wastewater (sewage effluent). Duckweed provides food for wildlife, especially waterfowl (Wetlands).” They will need to be placed in water immediately after opening. Grows vigorously. Ideal for providing cover for your fishes and excellent as a spawning media.) Duckweed will usually out compete algae. You rarely get green water in a tank covered with duckweed. Goldfish, too. Goldfish (and koi) also love duckweed. They inhale it like a Hoover. You will not keep duckweed in a goldfish tank. Laxative Powers. Nothing gets a goldfish moving cleans their intestines overnight, great for swim bladder problems. you’ll see a few remnants that tell you they love the taste of duckweed. Duckweed grows fast, therefore it needs lots of nutrition — exactly the same things your fishes give off — ammonia, nitrites, nitrates, phosphates, and carbon dioxide. Oscars, and other tropical fish stay healthy when they live under a thin carpet of duckweed. I say thin because duckweed will grow an inch thick if you let it get out of hand. Too thick a layer makes it hard to see your fish. It darkens your tank. Duckweed thrives in manure-rich waters and in excessively warm waters. It doubles in leaf area in three to four days. Duckweed grows incredibly fast.