Echinodorus tenellus is a synonym of Helanthium tenellum, the pygmy chain sword, which is still often called by this name in the aquarium hobby.12 Its range extends from the central and eastern USA to north-eastern Argentina.2 It grows on river and marsh margins, also in shade but more often in sun, in the Pantanal for example on seasonally flooded ground.1
The delicate, low-growing plant quickly forms stands by means of runners; a closed lawn in the foreground develops above all in bright light.13 How far the narrow submersed leaves shift from mid or olive green towards reddish depends on the light.34 The form traded as “parvulum”, probably North American and rare today, has somewhat broader, always light green leaves.134 Hard, alkaline water suits it less well than soft to moderately hard, slightly acidic water; fine sand or gravel suits its delicate roots.1
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