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Helanthium Tenellum  

Helanthium Tenellum

Updated on July 28, 2022
Reviewer Profile Photo
Reviewed by Don Spaeth
Petco’s National Aquatic Care, Education and Programs Manager

Appearance | Plant care | How to plant | Maintenance | Common problems | Propagation | Aquarium mates

Helanthium Tenellum

Helanthium tenellum is an aquatic carpeting plant that is prized for its natural, lawn-like appearance and relatively easy maintenance. It is also commonly referred to as pygmy chain sword or hairgrass, and it was previously known by the scientific name Echinodorus tenellus. By any name, this hardy, vibrant plant can be good for both beginner and experienced aquarists.  

Appearance  

Helanthium tenellum has narrow, oval-shaped leaves that taper to a point at each end. The leaves generally grow about one to three millimeters wide and up to three inches high—although they can grow higher in low-light conditions. From a distance, your Helanthium aquarium carpet will look like a dense lawn covering the bottom of the habitat.  

 Like a lawn, the leaves of Helanthium tenellum are usually bright green, but the tips of the leaves can also turn dark purple or red if given enough light and nutrients. It can also grow emersed—partially above the surface of the water—and can even thrive in terrariums if there is enough water in the soil. In both cases, the plant may sprout small white flowers about three millimeters across, which won’t grow when the plant is fully submerged.  

Plant care 

The Helanthium aquarium plant is relatively low-maintenance, as it’s considered hardy and undemanding. Its small size also means it can be grown in nearly any size enclosure, including nano aquariums. In a nano aquarium, you may need to prune it more frequently, while in larger aquariums, you may need stronger lighting to reach these plants at the bottom.  

 Like many aquatic plants, Helanthium tenellum does well with a pH range of 6.0 to 8.0. Its acceptable temperature range is also wide—about 72 to 80 degrees Fahrenheit—and it likes moderate to high full-spectrum lighting with a color temp around 6500 Kelvin for about eight to ten hours per day. However, it can also grow in colder temperatures and low-light conditions—it will simply grow more slowly and will not be as colorful.  

 Helanthium tenellum can be grown in either hard or soft water, and it tolerates higher water hardness up to 350 ppm GH. It doesn’t require added CO2, but like most aquatic plants, it will grow faster and show more vibrant colors if you add CO2 to the water through supplements or a pressurized system. Also, like many other aquatic plants, this one does well with a substrate depth of about two inches. It prefers soil-based substrates, although it can be grown in sand or fine gravel with additional supplements.  

While Helanthium tenellum care is relatively easy, it’s important to introduce it only to a stable and established aquarium. If the water parameters change too quickly or too drastically, it won’t be able to adapt and may die. Be sure you’ve fully cycled your aquarium before adding Helanthium tenellum. Check out our Aquatic Plant Care Sheet to see the supplies you need.  

How to plant it 

With a few considerations, Helanthium tenellum planting is nearly as easy as its care. At Petco, we offer many live plants and accessories, including  Helanthium tenellum, which is sold as a farm-raised tissue culture plant that you won’t need to quarantine.  

 To plant this aquatic flora, prune any damaged, yellow or brown leaves with pruning scissors. The plant typically comes in bunches, with several leaves growing out of each root system. Place each plant group deep enough into the substrate so the roots are well-covered. The roots are delicate—be cautious and use planting tweezers if necessary. Each bunch should be about an inch or two apart, depending on how dense you want the carpet to be.  

 In your aquascape, Helanthium tenellum plantings are most often placed in the foreground of the aquarium, with taller plants in the back. With good lighting and nutrients, they will quickly shoot off runners that will fill in the gaps between plants and create a beautiful green carpet. The runners can even grow over small rocks and driftwood, appearing to climb up the hardscape. The versatile Helanthium tenellum can also be cultivated between other plants for a natural or textured look or combined with artificial aquarium plants for a low-maintenance landscape.  

Helanthium tenellum care and maintenance 

Helanthium tenellum is a fast-growing, durable plant that is good for beginners but also admired by experienced aquarists for its compact, dense carpet growth. In nature, it grows in bog-type environments from the northern United States down to Paraguay in South America, and it can adapt to many different environments. However, one important piece of Helanthium tenellum care is pruning.  

 Because Helanthium tenellum grows so quickly, it requires pruning to prevent it from overtaking other plants if used as a carpeting plant. If you notice it sprouting very tall blades that stick out from the others, trim them back. If it begins to grow into parts of the aquarium where you don’t want it, you can cut it off at the roots or runners. Be sure to collect and dispose of all the trimmed foliage so it doesn’t sit in your aquarium and decay.  

 Helanthium tenellum also needs plenty of nutrients to nourish its extensive root system. You can add liquid fertilizers with macronutrients to the water column or root tabs around the plant’s substrate. Otherwise, Helanthium tenellum care is like any other plant for your aquarium. Be sure to maintain good water quality with regular, partial water changes and provide ample full-spectrum lighting and CO2 and this sturdy plant should do just fine.  

Common problems  

Its adaptability doesn’t mean Helanthium tenellum never has any problems. The most common issue is melt, which is caused by changes in the water quality and lack of nutrients. The leaves of the plant will appear transparent and eventually disintegrate altogether. Melt can be prevented by maintaining water quality and avoiding drastic changes—once melt has begun, you may need to replant your Helanthium tenellum. 

 If the leaves of your plant are turning yellow—rather than white or transparent—the issue may be a nutrient deficiency. Helanthium tenellum typically needs trace elements of iron and manganese in the water, as well as other nutrients. You can use supplements created specifically for planted aquariums and more general solutions like macronutrients and root tabs to reverse discoloration.  

 If your Helanthium tenellum isn’t growing as quickly as you’d like, you can try increasing the light intensity or providing it with more CO2 and nutrients. Relocating Helanthium tenellum plantings can also be difficult. When established, their root systems are large and typically cannot be moved.  

Propagation 

Unlike relocation, Helanthium tenellum propagation is fairly simple. Its runners can generally grow up to 20 inches long and shoot out plantlets—or new bunches of leaves—every inch or two. Remembering that the root system is very delicate, you can gently detach the plantlets from the runners and replant them wherever you want in your aquarium.  

Aquarium mates and compatibility 

Because of their delicate root systems, Helanthium tenellum does not do well with destructive or aggressive aquatic life, including larger cichlids and goldfish, which are notorious for uprooting live plants. Herbivorous fish like silver dollar tetras—as well as some species of larger snails—may eat live plants and should be avoided, as should destructive invertebrates like crayfish or crabs. 

What can you add to your Helanthium aquarium? Small community species like tetras, mollies, zebra danios, platys, minnows, guppies, rasboras, killifish and pencilfish are all good options. And while larger cichlids are not a good fit, dwarf cichlids like gold and blue rams should do fine. Certain algae eaters are also excellent choices, including dwarf shrimp and otocinclus catfish. They can even help keep your live plants healthy by eating trapped fish food, biofilm and algae.  

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