Helanthium tenellum (Pygmy Chain Sword)

Helanthium tenellum - pygmy chain sword

Last updated on July 8th, 2022 at 04:22 pm

The pygmy chain sword, Echinodorus tenellus, also known as Helanthium tenellum, is part of the aquatic plant family (Alismataceae) and originates from the Amazon River basin in South America. Echinodorus tenellus will grow to become an attractive and hardy aquatic plant that requires very little maintenance to grow and thrive once it has been planted properly.

A small, hardy, and easy-to-grow aquarium plant that’s great for beginners and experienced aquarists alike, helanthium tenellum (pygmy chain sword) has been popular in the aquarium hobby since its introduction in the 1950s. It’s also known as Echinodorus tenellus or small pygmy chain sword.

The beauty of this plant lies in its diminutive size, which makes it perfect for nano aquariums or even aquariums with a small footprint. Learn more about helanthium tenellum (pygmy chain sword) care and species profile below.

Caution: Helanthium tenellum (pygmy chain sword) is an invasive species and should not be released into the wild in the United States. It spreads quickly and can displace native aquatic plants, particularly in smaller bodies of water such as ponds and streams, by growing over them and out-competing them for nutrients, light, and space.

It also has the potential to change the pH of its new environment, making it impossible for some species to survive there any longer. If you must have one in your pond or aquarium, make sure that it doesn’t have any seeds!

Helanthium tenellum description

Helanthium tenellum - pygmy chain sword

The pygmy chain sword is an excellent aquarium plant for beginners and expert aquarists alike. It’s extremely adaptable, has no special lighting requirements, and comes in a wide variety of colors—and they’re all spectacular! The pygmy chain sword grows best when planted close to each other. Their trailing roots are fragile; try not to get them tangled together. Trim away any dead leaves with sterile scissors if you notice fraying in your tank.

They do well with weekly fertilization. And unlike some plants that look better floated, Echinodorus tenellus looks great when submersed—like it would be underwater in its natural habitat. Keep water temperature between 65-72 degrees Fahrenheit, KH level around 5, and pH level between 6.2-6.8 to grow healthy pygmy chain swords!

Origin and descriptions

Helanthium tenellum is a dwarf variety of chain swords (Echinodorus tenellus), and like all species in its genus, it originates from South America. It was only introduced to Europe at the beginning of the last century and was often confused with Echinodorus repens for several decades.

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In the 1950s, it was discovered that two types of pygmy chain swords were in fact two distinct species, and since then, Helanthium tenellus has been successfully used as an aquarium plant worldwide. Like most plants in its family, Helanthium tenellus produces offshoots easily; many aquarists who got their hands on some of these will be happy to tell you they’ve found ways to make them grow into full-sized specimens without too much effort.

Species profile

Helanthium tenellum - pygmy chain sword

An easy to care for aquarium plant, pygmy chain sword (Echinodorus tenellus), is one of the most popular species in home aquaria. The plant has bright green leaves and if kept under high light, will become red or purple in color. Pygmy chain sword is commonly sold under its abbreviation, H. tenellus; or as water sprite or a variant of water sprite with pygmy preceding it.

The Pygmy chain sword is a grass-like aquatic plant that grows to between 1 and 2 feet in height. When grown submerged in water, it can attain heights of 3 feet. Its flowers are tiny white blooms that grow on green, string-like strands above its foliage and stick out like spokes on a wheel. Like all plants within the Echinodorus genus, they reproduce by taking root fragments known as pups and establishing themselves nearby.

If you find new shoots sprouting up around your pygmy chain sword, they should be allowed to grow; they will not harm your main plant but will make an attractive addition to your aquarium design. They prefer plenty of light, so place them near the top front of your tank where they get direct sunlight during daylight hours.

They also enjoy high carbon dioxide levels, so if you have an airstone you should set it up directly over your planting area to ensure their growth does not become stunted due to the lack of CO2 available for photosynthesis purposes.


Helanthium tenellum - pygmy chain sword

Like other dwarf species, the pygmy chain sword can be propagated by the division of clumps. If you intend to propagate your Echinodorus tenellus, it is best to wait until your plant has produced a good number of leaves. Then, find a healthy spot in your aquarium where you would like to place new plants and trim off any long roots. With clean pruning shears or scissors, make sure that each cut is as clean as possible.

Next, place them in buckets with aged water or potting media, if possible, and allow them to sit for 1-2 weeks. Plants will begin to grow new roots and leaf growth within those two weeks; at that point, they are ready for planting in your aquarium.

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Alternatively, you can leave an inch or so of root attached when trimming to speed up their recovery time in pots. Leave plants inside buckets for several more days after they have begun growing new roots before transplanting them into your aquarium again.

Echinodorus tenellus care

Helanthium tenellum - pygmy chain sword

It is important to note that pygmy chain sword requires slightly different care than other aquatic plants. It prefers its water to be soft and slightly acidic, ranging from 5.5-7.5 in pH and dKH respectively. The temperature of your tank should not exceed 75°F, and it must be kept in low light conditions with minimal current or agitation. If you keep these things in mind, your pygmy chain sword will thrive!

The very first thing you want to do when acclimating a new specimen is placed it into a bucket or sink of dechlorinated water for an hour, just as if you were moving it from one aquarium setup to another. You also might want to gently rub off any algae present on the plant’s blades so they don’t continue growing and inhibiting photosynthesis once planted in your substrate.

Light requirements

Helanthium tenellum does well in moderate light but needs a lot of light to survive. It is recommended to place it near a window for at least 4-5 hours per day. Do not expose it to direct sunlight and keep it from drafts. If your room has low lighting conditions, you may have trouble growing the plant successfully. However, with enough light, you will be able to enjoy its golden color and delicate texture year-round!

Soil/potting mix

Helanthium tenellum, or pygmy chain sword, is native to South America. They require moist soil and indirect sunlight when grown indoors. If grown outdoors, they should be planted in a boggy or partially submerged area. The plant does not grow well if transplanted once it is mature, so be sure to start them from cuttings or divisions early on.

Another method is to submerge a pot containing Helanthium tenellum plantlets into an aquarium until plants can establish themselves in your garden beds. Be aware that if your plants become waterlogged for too long, they may rot and die.


This popular houseplant is one of two plants commonly known as pygmy chain sword. While often confused, Helanthium tenellum has been scientifically proven to be a separate species from Helanthium pusillum. The two plants are not poisonous but share similar characteristics—their leaves are linear and grass-like, and both live in wet areas along streams and bodies of water.

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Helanthium tenellum prefers more moisture than its relative; however, it can be grown with slightly drier soil as long as you keep it moist while actively growing. It’s less finicky than many other aquatic plants; thus if you have cats or dogs that might drink out of your fish tank, then Helanthium tenellum would make an excellent addition to your home. Though more delicate when young, it can take several years for Helanthium tenellum to become fully rooted in its potting material.

A thin layer of gravel on top will help maintain proper humidity levels around its roots until they get established, which may take about three months after planting. Continue watering throughout winter for established helanthium tenellum, but reduce watering during dormancy periods unless temperatures are above 55 degrees Fahrenheit at night. If temperatures drop below 50 degrees Fahrenheit, remove the plant from its current location to prevent cold shock damage to it.


Helanthium tenellum are aquatic plants, so for optimal growth, you’ll need to fertilize. If you’re looking for a balanced fertilizer with trace elements such as iron and zinc, look for a 10-10-10 NPK mix. While some brands sell specialized aquatic plant fertilizers, ordinary lawn fertilizers can also be used to keep helanthiums healthy. Remember that too much fertilizer can promote algae growth and result in cloudy water or other issues.


Helanthium tenellum is a tropical plant, so you’ll need to keep your plant warm. The ideal temperature range for this plant is between 70 and 85 degrees Fahrenheit. If your home falls below these temperatures in winter, consider getting a tank or cool-white fluorescent light to provide some extra heat.

During the summer months, avoid exposing your plant to high levels of direct sunlight for prolonged periods of time; an east-facing window works well. Avoid drafty areas near doors and windows where cold air can rush into your home.


Helanthium tenellum thrives in higher humidity, around 70%. On average, it should stay between 55 and 80%. But that doesn’t mean they don’t appreciate a little air conditioning on those incredibly hot days. Just make sure to check on your Helanthium every day or two; even though they are plant hardy, they still need some TLC.


After your Helanthium tenellum reaches 3’, it will start to form loose rosettes of small leaves. This is normal and indicates that you should begin pruning it. Simply pinch off each rosette by hand to promote new growth from its center.

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This will also encourage new leaves to branch out from each leaf node, which in turn increases photosynthesis and improves plant health. Perform pruning once a month during spring and summer months, then every 2–3 weeks during fall and winter.

And be sure to do it underwater! If you don’t own a fish tank or bowl, fill a container with water using a quarter-strength solution of liquid houseplant fertilizer; fish waste helps boost nutrients for plants. Then, gently remove each spent flower before placing your swords into their containers; don’t worry about damaging them—they actually prefer to be handled roughly because they are so flexible!

Growth rate

Helanthium tenellum is a fast-growing plant that typically experiences a quick burst of growth within 1–2 weeks and continues at a steady rate until full maturity. After 4–6 weeks, it reaches its maximum size. This means that if you have limited space for your aquarium and would like to keep Helanthium tenellum, be sure to plan ahead for its future growth by choosing an appropriately sized pot or container.


Helanthium tenellum is not known to be toxic. This species is often confused with other Helanthium spp., which are in fact toxic. There are no harmful side effects from handling or growing pygmy chain sword.

If a plant acquired by you under another name is suspected of being potentially toxic, do thorough research for that plant, including toxicity or poisoning as keywords. It will tell you what plants look like and anything else you should know about their toxicity. You may need to contact your local poison control center for more information if it turns out your plant is indeed toxic and would make a good story… just don’t forget to tell them how your beloved aquatic died so tragically!

Pests and diseases

Helanthium tenellum is susceptible to a variety of pests, including aphids, mealybugs, scales, and thrips. Scales can be particularly problematic for pygmy chain sword plants. They appear as small brown or white bumps on leaves and stems; they produce honeydew which then attracts ants and mold spores that might make your plant sick. In some cases, you may need to treat your entire aquarium for a scale infestation.