Eleocharis Acicularis (Dwarf Hairgrass/Needle Spikerush)

Eleocharis acicularis

Last updated on July 4th, 2022 at 10:26 am

Eleocharis acicularis, also known as Dwarf Hairgrass, is one of the most common aquatic plants in the aquarium hobby, but it can often be challenging to care for it correctly. They can be an attractive addition to freshwater aquariums with proper care and maintenance.

Also called needle spikerush, eleocharis acicularis is an aquatic plant species that has become quite popular in the aquarium trade in recent years, though it has been used as an aquarium subject for many decades. Despite its popularity, there are many facts about this attractive and easy-to-grow species that are not known to aquarists who have not kept it before.

Wherever you live, it’s likely that you have come across the grass species Eleocharis acicularis before, as it’s commonly used in aquarium tanks by beginner hobbyists and experienced aquarists alike. In fact, it’s one of the most common aquarium plants that most people will come across at some point in their lives, and also one of the easiest to grow and maintain in an aquarium setting if cared for properly.

The dwarf hairgrass, consists of many small plants that grow in short tufts on top of the substrate in an aquarium, as well as in shallow waters and backwaters of ponds and lakes. The plant grows in both acidic and alkaline water conditions and requires moderate light levels.

Origin and descriptions

Eleocharis acicularis

Eleocharis acicularis is a freshwater aquarium plant native to Sri Lanka. It belongs to a group of aquarium plants called sedges. It is sometimes also referred to as Elkhorn grass because of its stiff, grass-like appearance. This needle spikerush grows well in freshwater aquariums with temperatures ranging from 72-86 degrees Fahrenheit, and pH levels of 6.5-7.8 are ideal for hairgrass growth.

Dwarf hairgrass is a slow-growing plant so it will take approximately 2 weeks to grow roots enough to remain planted after transplanting. When grown properly, Eleocharis acicularis reaches about 5 inches tall and has relatively small leaves that closely resemble grass blades. Its color depends on how much light it receives but typically ranges from bright green to olive green colors on top with yellowish-brown root coloring underneath.

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Because of its ability to grow quickly, some people choose to divide their plant every few months making keeping dwarf hairgrass an easy task even for beginning aquarists.

Species profile

Eleocharis acicularis

Eleocharis acicularis, or dwarf hairgrass, is an aquatic plant in the sedges family Cyperaceae. It is native to North America, where it grows in shallow water. The plant has about 10 to 20 leaves per stem, each leaf measuring up to 0.3 inches long by 0.05 inches wide. The flowers are light brown and have a diameter of less than 0.04 inches; they are arranged into spirals around 1 to 2 feet above the base of stems. The fruit is formed within a capsule that measures around 1 inch long by half an inch wide.

Dwarf hairgrass scientific name

The scientific name of the dwarf hairgrass plant is Eleocharis acicularis

Dwarf hairgrass height

Since it is called dwarf hairgrass, this plant don’t grow very tall, reaching a maximum height of about 5 inches (13 cm).

How to grow dwarf hairgrass

Eleocharis acicularis

Dwarf hairgrass is easy to propagate from either side shoots or rhizomes. The easiest way to propagate dwarf hairgrass is to simply divide any clumps that become too large. To divide, simply pull apart clumps of grass with your hands. They will naturally divide into smaller pieces once you’ve removed them from their original pot.

Clumps can be divided in half again after they have been replanted in their new pots. Some aquarists prefer to use a sharp razor blade to divide larger plants.

If a plant has numerous small offshoots at its base, it can be divided by cutting off each individual shoot with a sharp razor blade or pair of scissors. Each shoot should then be placed in its own container filled with moist soil before being planted in an aquarium; make sure each plant receives at least two watts per gallon for optimal growth rates.

Eleocharis acicularis grows quickly if properly maintained and will soon fill out any empty spaces within an aquarium. When pruning these algae eaters, always trim just above where a node occurs, otherwise, you risk damaging or even killing your aquatic ferns. Nodes are typically located right above where roots extend down into the substrate of an aquarium.

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Roots usually grow just beneath nodes because they need access to nutrients within the substrate during photosynthesis.

Dwarf hairgrass care

Eleocharis acicularis

Eleocharis acicularis needs bright, indirect light. It will do fine in medium to low light conditions, but if you don’t have a spot with enough light, grow it under fluorescent lighting. Keep your tank on a substrate of at least 4 inches of sand. The sand will help hold oxygen and give your plant some structure to grow on. Make sure you keep nutrients at 0 ppm as well; too much fertilizer can kill Dwarf Hairgrass quickly!

Dwarf hairgrass light requirements

Dwarf hairgrass grows in shade, partially light and full sunlight. Keep in mind that not all light is equal. For example, sunlight through a kitchen window differs greatly from light shining into your living room in midday. When you first acquire Eleocharis acicularis, it’s best to place it in a location where it will get as much direct sunlight as possible during daylight hours; once established, you can move it into the partial shade or full shade if necessary.

If you live in an area where temperatures rarely drop below freezing, such as North Carolina’s Research Triangle Park, then any amount of light might be sufficient—but keep in mind that extremes also affect plant growth. Just because temperatures remain moderate year-round doesn’t mean aquatic plants like Eleocharis acicularis won’t suffer if they go too long without being moved back indoors or exposed to extreme heat outdoors for extended periods of time.

Substrate/Soil requirements

Depending on your species, Eleocharis acicularis likes wet or dry substrate. It is an emergent species that prefers to grow in shallow water with a good amount of oxygen; however, it can also grow in dense beds of soil. It does not like to be kept moist all the time, as it can lead to bacterial and fungal infections in higher concentrations of oxygenated water.

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I recommend keeping 4-6 inches of the substrate under each pot if you are keeping them submerged. Under normal conditions, many growers will plant them right up to their leaves or submerge roots slightly below ground level to prevent tip burn when they’re placed above the waterline.

Needle spikerush fertilizer

Because it doesn’t have rhizomes, Eleocharis acicularis doesn’t need to be fertilized as often as most other aquarium plants. It also grows very slowly; in a 10-gallon tank, it might only grow a couple of inches over an entire year.

Overfeeding is one of the biggest dangers for aquarists who house dwarf hairgrass, so stick to its recommended doses when dosing your aquarium’s water with fertilizer. Once every two weeks should be enough for most situations.


Eleocharis acicularis is an extremely adaptable aquarium plant. It can survive a wide range of water conditions from pH 2.0 to 8.0, hardness up to 14 dGH, and temperatures from 18-34°C or 64-93°F without showing any signs of distress. However, its adaptability does not mean it will thrive in these conditions—the plant merely survives them.

Eleocharis acicularis humidity

The water level in a container should be kept between 30 and 70%, which equates to a 1:3 to 1:5 ratio of soil:water. Ideally, you should measure your soil’s moisture levels at least once per week using a moisture meter or stick that can be purchased at your local garden store. Remember, drought-tolerant plants do not like to be overwatered!

Pruning the needle spikerush

Eleocharis acicularis

During times of low light, you can prune your Eleocharis acicularis to stimulate new growth. As these plants grow close to each other, it’s common for stems to be bent over or even tangled together. To separate them, use tweezers to gently tease them apart. If you have a very large aquarium, you may need to divide your population by cutting off an entire section of stems and planting it in a separate container.

If you choose to do so, make sure that both containers are at least 5 gallons as there is often a high die-off rate when moving between containers. You should also consider replacing about half of your water with fresh dechlorinated water during any such transplantation process.

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Dwarf hairgrass growth rate

Dwarf hairgrass has a very fast growth rate. They grow best when provided with abundant light, nutrients, and CO2. As a result of its rapid growth rate, it is highly recommended to fertilize dwarf hairgrass once per week with a fertilizer designed for aquarium plants.

USDA hardiness zones

This plant is hardy to zones 9b-11. Zones 10+ will have no freezing temperatures; therefore, you can plant year round in zone 10+. Although dwarf hairgrass will grow in most areas of zone 8, we don’t recommend planting it during these cold months.


Not toxic. In general, aquatic plants are safe in a well-established aquarium as long as they are not allowed to grow out of control. A few exceptions include Water Hyacinth, which spreads quickly and can easily take over an aquarium; Green Cabomba, which is believed to release chemicals into water that cause skin irritation; Indian Almond Leaves (stems secrete mucilage); Swiss/American Pondweed, native to parts of Asia but invasive in some US waterways; Wild Radish – Can become invasive in some areas.

Pests and diseases

One of two major problems for Eleocharis acicularis is likely to be pests, particularly if it grows in an area that has a lot of sun. Chlorophyllum molybdites is a common fungi pest of dwarf hairgrass that causes tiny black spots on leaf surfaces. If you see these growing on your plant, remove them as soon as possible, or they will spread throughout your tank and cause harm to other plants as well.