Eleocharis acicularis
The taller sister of dwarf hairgrass, needle-thin blades reach 10–20 cm. Forms a 'grass field' look behind a foreground rather than a flat carpet. Tolerates cooler water than parvula; pairs with white clouds and hillstream loaches in unheated tanks.
Needle Hairgrass (Eleocharis acicularis) is a carpet / runner aquatic plant for the foreground to midground of a planted tank. It reaches 10–20 cm under good conditions and grows at a medium rate. Light: low to high. CO₂: optional. Target 18–26 °C, pH 6.0–7.5, and 2–15 dGH. Substrate: Fine nutrient-rich substrate + root tabs. Propagate via runners.
Care at a glance
The taller sister of dwarf hairgrass, needle-thin blades reach 10–20 cm. Forms a 'grass field' look behind a foreground rather than a flat carpet. Tolerates cooler water than parvula; pairs with white clouds and hillstream loaches in unheated tanks.
By Mike ElmiraUpdated 2 min read
Part of our complete guide to the planted aquarium.
Hero photo by Kristian Peters -- Fabelfroh 07:18, 1 July 2007 (UTC) · CC BY-SA 3.0 · Wikipedia
The parameters that decide whether needle hairgrass fits in your tank.
Cyperaceae
Carpet / Runner
Foreground to Midground
Fine nutrient-rich substrate + root tabs
Runners
Damp shorelines of temperate ponds and seasonal pools
Worldwide temperate
Tank-mate safety and the species this one is documented to thrive (or fail) alongside.
Hard-won lessons from the tank.
Plant 2x2 cm portions in a grid 3 cm apart. Carpet completes in 8–10 weeks with CO₂, 14+ weeks without. Pairs with parvula (lower carpet) in foreground and shorter chain sword (midground) for a layered 'meadow' effect. Cool-tolerant — works in unheated tanks with white clouds.
What can go wrong and how to spot it.
Failure modes, in order of how dramatic the fix is.
Brown tips: iron or CO₂ insufficient. Slow spread: low light or substrate nutrients. Pale: nitrogen + iron.
Hair algae loves the fine leaves. Stable CO₂ and limited light hours during establishment prevent it.
The practical routine, read top to bottom.
Moderate root and column feeder. Root tabs every 4 months. Iron and macro dosing accelerate spread. CO₂ helps but not required.
Trim every 4–6 weeks to encourage horizontal runner spread. Aggressive trimming pushes the plant to carpet rather than grow vertically.
Where it comes from, how it behaves, and the variants you'll see at retail.
Where it lived before it came home.
Pond margins, slow streams, and seasonal wetlands across temperate regions worldwide. One of the most cosmopolitan aquatic plants.
Compact emersed clumps. Wholesale arrives emersed via tissue culture; transitions to submerged form with longer finer leaves.
Tiny inconspicuous emersed flowers; never flowers submerged.
The named cultivars and the lookalikes worth flagging.
E. acicularis (standard, 10–20 cm), E. parvula (dwarf hairgrass, 5–10 cm — already in catalogue), E. vivipara (very tall, 30–60 cm). All similar care, varying mostly in height.
E. acicularis and E. parvula are often confused at purchase — parvula stays 5–10 cm even mature; acicularis reaches 15–20 cm. Buy from a knowledgeable source.
Direct answers to the questions search engines and AI assistants surface most often about this species.
CO₂ requirement: optional. Light requirement: low to high. Under low-tech conditions the plant grows at a medium rate.
Needle Hairgrass (Eleocharis acicularis) needs low to high light. Run a photoperiod of 6–8 hours; longer photoperiods invite algae unless CO₂ and dosing are dialled in.
Position: foreground to midground. Substrate: Fine nutrient-rich substrate + root tabs It typically reaches 10–20 cm.
Propagation method: Runners. Needle Hairgrass is a carpet / runner plant.
Target 18–26 °C, pH 6.0–7.5, and 2–15 dGH. Flow tolerance: low to medium.
Difficulty: 2/5. Forgiving, beginner-friendly once the tank is cycled.
A planted tank is a system. Pair this plant with one entry from each other pillar to plan the whole scape.
