Spirodela polyrhiza, or greater duckweed, is distributed in almost all the world in temperate to tropical climates. It is also found in Central Europe, frequently together with other duckweed specis, mainly in stagnant, eutrophic (= nutrient-rich), shallow, muddy waterbodies. Spirodela is only found in some locations in South America, its main representative there is Spirodela intermedia, whose area of distribution is limited to Central and South America.
The plants of the genus Spirodela are the largest duckweeds. They differ from similar genera (Landoltia punctata, Lemna species) by its about 1 cm large round fronds, with a reddish underside and tufts of many roots (7-21). Landoltia punctata has a tuft of only 2 to 7 roots, duckweeds of the genus Lemna only have one root per frond.
As floating plant in the aquarium, Spirodela polyrhiza grows as well as all other duckweeds, especially if the water is rich in nitrate, phosphate and potassium. It only needs moderate light. Its size makes its control easier to manage than other duckweeds.
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