How to grow Eleocharis acicularis [Dwarf Hair grass]

Introduction

Eleocharis acicularis, commonly known as dwarf hair grass or needle spikerush, represents one of aquascaping's most versatile and enduring carpeting plants. This sophisticated aquatic species transforms ordinary aquarium substrates into lush, meadow-like landscapes that rival terrestrial grasslands in their visual appeal.

Eleocharis acicularis belongs to the Cyperaceae family, a group of sedge plants characterized by their grass-like morphology and specialized adaptations for aquatic environments. The species name "acicularis" derives from Latin, meaning "needle-shaped," which accurately describes the plant's distinctive blade structure.

This perennial sedge exhibits remarkable morphological plasticity, growing 10-15 centimeters (4-6 inches) in height under submerged conditions, though terrestrial forms may reach up to 30 centimeters. The plant's most striking feature consists of thin, hair-like stems measuring 0.2-0.5 millimeters in diameter, often displaying 3-12 angular ridges that provide structural support. These needle-like blades emerge from a creeping rhizome system that spreads horizontally through the substrate, enabling the plant to form dense colonial mats.

The species has enjoyed a lengthy history in aquarium cultivation, with commercial availability dating back several decades. What exactly constitutes its enduring appeal lies in the plant's dual nature—capable of growth both submerged and emersed, making it suitable for traditional aquascapes, paludariums.

Differentiating between Eleocharis species

Eleocharis acicularis often faces confusion with its closely related cousins, particularly E. parvula and E. pusilla (frequently sold as E. parvula mini). Although these species share morphological similarities, key differences distinguish them for the discerning aquarist.

E. acicularis typically grows taller than E. parvula, reaching 10-15 centimeters compared to E. parvula's maximum height of 5-7 centimeters. This results in E. acicularis displaying a more upright growth pattern, while E. parvula exhibits more horizontal, creeping characteristics. Furthermore, E. acicularis demonstrates greater tolerance for varying light conditions, whereas E. parvula demands more consistent high-intensity illumination for optimal carpeting.

The leaf blade structure also differs subtly—E. acicularis maintains straighter, more rigid blades that sway gracefully in water currents, while E. parvula produces softer, more curved blades that create a denser, more compact carpet appearance. However, these differences become less pronounced under optimal growing conditions, leading to frequent misidentification in commercial settings.

Aquarium Placement and Aquascaping Applications

Eleocharis acicularis functions primarily as a foreground plant, although its moderate height allows for creative midground applications in larger aquascapes. This versatility makes it an exceptional choice for multiple aquascaping styles, from minimalist Iwagumi layouts to complex Dutch-style arrangements.

In Iwagumi aquascapes, E. acicularis is commonly used to create sweeping grass plains that emphasize the hardscape's dramatic stone formations. The plant's natural growth pattern produces subtle height variations that add depth and movement to these otherwise stark compositions.

Substrate light levels measure between 30-50umols of PAR in this tank.

How to grow

There are two approaches to growing this plant. In non CO2 injected tanks, higher light levels are more effective, to compensate for the lack of CO2 availability while in CO2 injected tanks, E. acicularis can be grown with much less light. In non CO2 injected tanks, 100umols of PAR is a good light level to grow the plant, while in CO2 injected aquariums, it can spread well in just 40 to 50umols of light. Carbon dioxide supplementation dramatically improves growth rates and carpet density. 

E. acicularis feeds well from the substrate and have a substantial root system. Using a rich  aquasoil allows the plant grow well without the need to saturate the water column heavily with fertilizer.

Planting in as small clusters as you can manage (down to clusters with less than 10 leaf blades) 2 to 4cm apart allows the carpet to spread evenly. Planting in larger bunches tends to give poor results as larger clumps tends to float easily and plants that are in the middle of the plant will suffer from over-crowding. Planting in smaller clusters allow individual plants to root properly, which in turn allows the carpet to grow and spread faster.

Substrate light levels measure between 40-60umols of PAR in this tank.

Insufficient lighting triggers etiolation, causing the plant to grow tall and spindly rather than developing the desired compact carpeting form. This response represents the plant's attempt to reach higher light levels, resulting in an undesirable "weedy" appearance.

It is very flexible with regards to water parameters and can be grown in both soft, acidic water and hard, alkaline water. Temperature tolerance is equally wide, spanning 15-30C +, making the species suitable for both tropical and temperate aquarium setups. 

E. parvula is shown here in our warm tank, that runs at a constant 31C.

Trimming and propagation

Dwarf hair grass can be mowed down with scissors as the carpet thickens. This can be done for a few trimming cycles. However, trimming top growth does not solve the accumulation of old roots that compacts the substrate zone over time with decaying organic material. This accumulation of organic debris will eventually affect growth and is often the reason older carpets get infected by algae.

The solution for long term maintenance comes in two choices. The first is to regularly remove small patches of plants in their entirety, including the root system rather than just trimming the top growth off. This can be done without creating a large mess in the tank by holding a water siphon at the spot where uprooting is done. The second choice is to let the root system accumulate over a longer horizon, then do a large removal and replanting when the carpet becomes too dense to grow in a healthy way.

Exotic alternatives

Centrolepis drummondiana also known as "Blood vomit" looks similar to dwarf hair grass with an attractive red base. However, it is much more difficult to grow. It does not spread through runners and grows at a fixed height. 

Click here to read on how to grow Centrolepis drummondiana

Click here to find out how to grow red aquarium plants.

Click here to read on how to optimize CO2 levels

Click here to browse more plant growing profiles

Click here to read on how to stabilize a new planted tank