Helanthium tenellum (Echinodorus tenellus)

Known to most older aquarists as 'Echinodorus tennellus', the "Pygmy Chain Sword" is a fantastic carpeting plant that has a distinctly organic and "casual" grassy appearance. It can be used to great effect in the foreground or midground of your aquarium.

Considered the "Smallest sword plant", it is also one of the oldest and most popular plants in the hobby for its versatility, beauty and uniqueness that is at home in any aquascape from the smallest nano aquariums to massive display tanks. It is probably the most commonly used foreground and carpeting plant because of its long history in planted aquariums. It remains popular today due its captivating appearance and relatively undemanding requirements. It was officially moved into the genus Helanthium in 2007 along with some other smaller, thinner leaf "swords". It is a highly versatile plant that can be grown without CO2 in medium-low light but takes on a dramatic appearance and unique growth habit with high light and CO2.

H. tenellum is a classic rosette plant in-between the appearance of Dwarf Sag (Sagittaria subulata) and Dwarf Hairgrass (Eleocharis acicularis). Its leaf blades are generally narrower than Sag and broader than Hairgrass. Under ideal conditions, it is a rapidly growing plant that creates very dense lawns through a prolific system of "runners" (technically stolons). It is a low-growing plant that rarely exceeds 5 cm submerged and does well in medium light with no CO2.

In high light with CO2, H. tenellum forms a dense turf on an extensive "cushion" of runners by which it spreads. While it can be grown beautifully in low-tech tanks, it certainly takes advantage of every bit of light and CO2 it gets. In lower light conditions, the plant will grow slightly taller but will very rarely exceeds 7cm in height.

This comparatively diminutive plant is similar in many ways to its cousins, the Amazon Sword Plants. It is a hardy and adaptable species with few specific requirements and tolerates a wide range of water conditions and temperatures. Helanthium tenellum, like all sword plants, is a prodigious root feeder and appreciates a nutrient-rich substrate (achieved with root tabs, specialty planted aquarium substrate or just  detritus deposited by fish and other plants). Since Helanthium tenellum develops and relies on a large network of ‘subterranean’ roots and stolons to grow and reproduce, a soft, fine grained substrate is best. Alternatively, a coarser but lightweight planted aquarium substrate is also suitable.

Though H. tenellum adapts easily to a wide range of conditions, it does prefer softer water that is slightly acidic. It can adapt to harder water, but pH should remain below 7.5 for best results. Luckily, this is the case for the vast majority of planted aquariums.

As for aquascaping, Helanthium tenellum is extremely versatile. In high tech tanks, it rapidly grows into large compact patches which can acquire a reddish appearance and quickly become a dramatic focal point. In low tech tanks, expect tamer patches where it is a great addition to the foreground. H. tenellum is often planted in front of, or between rocks and driftwood where it creates a soft, natural effect as if a lush forest had grown around some worn boulders and fallen trees.

Dense lawns of tenellum can take on a characteristic "tussled" look that is extremely striking and contrasts beautifully with plants that grow in a more uniform fashion.

Placed slightly behind even shorter carpet plants such as Glosso, HC Cuba, ‘Monte Carlo’ or UG (1), a patch of Pygmy Chain Swords will add dramatic depth and dimension. H. tenellum is also incredibly useful in nano aquariums where its small size creates illusions of scale and perspective.

This very small, thickset, plant looks absolutely stunning with shrimp or colorful schools of fish. Dense stands of tenellum quickly becomes a great micro-habitat for baby shrimp, fry or shy fish seeking shelter and protection.

Botanically, Helanthium tenellum is an astonishingly wide-ranging species native to freshwater bodies throughout the Americas. It can be found from Paraguay to the Amazon, all the way north to the Great Lakes and Canada. As of 2020, it is considered an endangered species in at least five northern US States in which it is native. Found in environments as different as Amazonian rivers and New England marshes H.tenellum has different varieties that differ in coloration, size, and leaf shape. At least two types are commonly available for planted aquariums.

Our Helanthium tenellum is a medium to dark green variety with thin leaves that is most likely endemic to equatorial South America. Under high lighting and good nutrition (particularly iron), this variety will produce young leaves with a reddish tint and is sometimes referred to "Bronze Pygmy Chain Sword".

Incidentally, we also carry the other, presumably more Northern variety (Helanthium tenellum 'Green') - with broader leaves and a lighter green color which does not significantly change. This variety may be hardier and less demanding but is equally cherished.

We wholeheartedly recommend H. tenellum togther with its ‘Green’ variant for anyone starting a planted aquarium or wanting an addition to an existing aquascape - with or without CO2. 

Varieties of Helanthium tenellum were featured in some of earliest planted aquaria at the dawn of color photography and remains as popular as ever despite the plethora of new plants that have become available to the hobby over those decades. While many other “founding plants” are rarely used today, the enduring popularity of the Pygmy Chain Sword is a testament to its value. Despite the name change, it is a real classic and almost a rite-of-passage for aquatic gardeners.

Like most aquarium plants, the Pygmy Chain Sword naturally grows on the margins of rivers, lakes, ponds, or marshes and, like virtually all aquarium plants, can be grown emersed in terrariums, paludariums or Wabi Kusa. Emersed parts of the plant will produce simple flowers on stalks. Out of the water, runners are rare and leaves will become broader and grow closer to the ground.

Like the most of our plants, ABC plants’ Helanthium tenellum is cultured in the submerged form for increased survival and rapid growth after being planted in aquaria but our cultures also acclimate to emersed growth very easily.

 

(1) The full names of the plants referred to are: Glossostigma elatinoides, Hemianthus callitrichoides ‘Cuba’, Micranthemum ‘Monte Carlo’ and Utricularia graminifolia respectively.