Lomariopsis lineata is a species of fern native to South East Asia.The prothallia of this species (or possibly a closely related species) are commonly cultivated as an aquarium plant, where it is known to aquarists as süsswassertang (German spelling: Süßwassertang). It is often incorrectly spelled “subwassertang” due to the German eszett’s similarity to the Latin ‘B’. It is also called Loma fern or round pellia. In the aquarium industry, it is commonly confused with similar-looking liverworts of the genus Pellia and Monosolenium.