Needle leaf hairgrass
Eleocharis acicularis
Also known asNeedle spikerush · Least spikerush · Dwarf hairgrass (tall form)
Water parameters
Light and nutrients
Substrate type: nutrient preferred. Propagation: runners.
Substrate compatibility
| Substrate | pH effect | Nutrient load |
|---|---|---|
| Aquasoil (ADA Amazonia) | lowers pH | very high |
| Mineralized clay substrate (Seachem Fluorite) | neutral / inert | moderate |
| Dirted tank (mineralized topsoil) (DIY soil substrate) | slightly acidic | very high |
| Inert sand (Pool filter sand) | neutral / inert | none |
With fish
Origin and habitat
A fine, needle-stemmed sedge of the family Cyperaceae, Eleocharis acicularis, the needle or least spikerush, widespread across the temperate Northern Hemisphere, through Europe, central and southeastern Asia and North America, and south into northeastern South America to about Ecuador, with introduced populations in Australia. It grows in marshes, vernal pools, bogs and pond margins as grass-like stems under a millimetre thick from a creeping rhizome. This is the taller Eleocharis sold in the hobby, reaching 10–20 cm submersed, distinct from the true dwarf forms E. parvula and E. pusilla that stay 5–10 cm. The very fine texture gives a soft, meadow-like look unlike the broader dwarf sagittaria or Helanthium.
Outdoor pond use
- USDA zones
- 5–10 (winter low around -29°C or warmer)
Care notes
Moderate care. It carpets best with bright light, which keeps growth compact and horizontal; in dim light it grows tall and vertical and loses the carpet effect. CO2 is optional but speeds and densifies coverage, closing a carpet in six to ten weeks with light, CO2 and nutrients, versus several months without. Its 10–20 cm height suits the midground more than a tight foreground carpet; for a low lawn use the dwarf forms. Plant plugs a couple of centimetres apart in fine gravel or nutrient-rich substrate, with root tabs in inert sand. It spreads by horizontal runners that root into new tufts, and trimming keeps it even and pushes lateral spread; thin old, thick stands that go bare at the base. A real strength is cold tolerance: it handles a wide range, roughly 4–28°C, and works in unheated coldwater tanks where most carpets fail. Keep soft to moderately hard water around pH 6.3 to 7. Algae can settle on the fine stems if nutrients or CO2 swing, and digging fish can uproot the fragile stems, so pair it with gentle species. It is an ornamental carpet, not a crop, so it is unsuited to media-bed aquaponics or hydroponics.