Helanthium tenellum (previously known as Echinodorus Tenellus before being reclassified) is a carpeting grass-like plant that looks like a cross between dwarf hair grass and micro swords. This plant spreads by sending out lateral runners, similar to hair grass and other swords, and can cover the foreground of your aquarium if grown properly. This plant can also be used as a short background plant in smaller nano tanks, but adequate lighting and CO2 are recommended.
The pygmy chain sword, Helanthium tenellum, grows as a bog plant from the northern United States through Central America to Paraguay, South America. It was previously known as Echinodorus tenellus, both botanically and in the aquarium hobby, but it is now classified as a Helanthiumspecies. Haynes and Holm-Nielsen assigned these plants to the subgenus Helanthium in 1994. Based on cladistic and molecular analysis, Samuli Lehtonen and Leena Myllys elevated the subgenus to the status of a full and distinct genus in 2007.
With such a wide range of distribution from North to South America, leaf shapes and sizes vary greatly. Aquarists typically see two distinct types. The most common narrow leaf variety has dark-green leaves that are only 1 to 2 mm (1/16 inch) wide and reach a height of up to 70 mm (3 inches). Given enough light and nutrition, new leaves can turn a deep red colour. The rarer broad-leaved variety has shorter, broader light-green leaves that are 4 to 5 mm (1/8 inch) wide at the base and taper to the tip, but it can grow up to 70 to 100 mm tall (3 to 4 inches). Even at high light intensities, this variety will not turn red.
H. tenellum is a low-maintenance plant that can be grown in medium to low light with no additional fertilisation or CO2. It can tolerate soft or hard water and pH levels ranging from 6.0 to 8.0, as well as GH values of up to 20 degrees/350ppm. H. tenellum spreads by runner chains (modified inflorescences) up to 50 cm (20 inches) long, with plantlets forming every 2 to 5 cm (34 to 2 inches) whether grown emersed or submerged. These plantlets can be separated and planted on their own. A nice and thick rapidly expanding turf can be expected in good light, with added CO2 and fertilisation. Low light, on the other hand, with no additional CO2 or fertilisation, will result in slower, sparser growth. Once established, H. tenellum may need to be pruned on a regular basis to keep it from invading the tank. When grown emersed, it will also produce flowers, but runner production is less frequent.
How should Helanthium Tenellum be pruned?
Many ground-covering plants, such as Helanthium tenellum and Eleocharis, reproduce by sending out creeping shoots. If you want to cut the leaves of a stoloniferous plant, perhaps because they have grown too long or too old, simply cut the leaves with a pair of scissors at any point. The remaining stumps wither away with time.
How do you cultivate Echinodorus Tenellus?
Although high lighting and CO2 injection are not required to grow Echinodorus Tenellus, they are highly recommended for faster and fuller growth. Simply cut larger mats into small pieces and plant each one an inch or so apart halfway into the substrate.