Giant Hairgrass (Eleocharis montevidensis) is a taller, more substantial hairgrass species than its dwarf counterpart — producing fine, upright, dark green blades that reach 20–40cm under good conditions and spread by runners to form a loose, naturalistic grass stand in the mid-to-background zone. It occupies a distinct niche from the Vallisneria species in the catalog: where Vallisneria produces broad ribbon leaves that move dramatically with current, Giant Hairgrass produces very fine, needle-like blades that barely widen beyond a few millimetres and sway with a lighter, more delicate motion in response to water movement. The visual quality is closer to riparian meadow grass than to the aquatic ribbon-leaf Vallisneria aesthetic — more restrained, more fine-textured, and more suited to layouts where a natural, understated grass background is the goal. Spreads by runners. Roots in substrate. Fully safe with all Neocaridina, Caridina shrimp, and snails.
Not RequiredCO₂
64–82°FTemperature
Low–MedLighting
What to Expect
Growth & Behaviour Over Time
Fine, upright dark green blades reaching 20–40cm — the defining quality of Giant Hairgrass versus Dwarf Hairgrass is simply scale — where Dwarf Hairgrass produces blades under 10cm suited to foreground planting, Giant Hairgrass produces blades at 20–40cm that fill genuine midground and background space. The blade width is similarly fine in both species — needle-like and consistently narrow — giving the taller plant the same delicate, hair-like quality at a substantially larger scale.
Spreads by runners to build a grass stand over time — established plants send out horizontal runners that produce daughter plants at intervals, gradually filling available background space with additional grass blades. The spread rate is moderate — Vallisneria spreads more aggressively, Giant Hairgrass more selectively — and the stand that develops has a loose, naturalistic quality with slightly irregular spacing that reads as more organic than a uniformly planted grass background.
Fine blades respond to current with subtle, delicate movement — the very fine, needle-like blades of Giant Hairgrass catch water movement with a lighter, softer response than the broad ribbon leaves of Vallisneria — a gentle trembling and swaying rather than dramatic sweeping. In tanks with moderate flow the movement is constant and subtly animated; in low-flow tanks blades stand relatively still and the upright, fine-textured mass reads as a static grass backdrop.
Roots in substrate — feeds primarily through root system — Giant Hairgrass roots into substrate and draws its nutrition primarily from there, making substrate quality the primary driver of growth rate and blade height. In nutrient-rich aquasoil or with root tabs the blades reach their maximum height and runners spread more actively; in inert substrate without supplementation the plant grows more slowly and blades remain shorter.
Does not require trimming in most tank sizes — unlike Vallisneria, Giant Hairgrass at 20–40cm maximum height does not reach the surface in tanks of standard depth (35cm or more) and does not require regular trimming to prevent surface cover. It grows to its natural maximum height and stops there, requiring only occasional runner management if spread exceeds the intended planting area.
How to Set It Up
Getting Started
1Plant in small groups in the mid-to-background zone — separate into individual blades or small clusters and push gently into substrate to 1–2cm depth, leaving the crown just at or above the substrate surface. Space initial plantings 2–3cm apart across the intended area — close enough that runners will knit the planting together within months but with enough space for each blade cluster to develop its natural form without immediate crowding.
2Use nutrient-rich substrate or root tabs — place root tabs at regular intervals across the planting area. Giant Hairgrass blade height and runner production are directly responsive to root nutrition — plants in well-nourished substrate reach significantly greater height and spread more actively than those in inorganic substrate without supplementation.
3Direct moderate flow across the planting for movement — position the filter outlet to produce a gentle-to-moderate current across the grass stand. The fine, delicate movement of Giant Hairgrass blades in current is the plant's primary visual quality in a layout context — without flow the blades are still and the grass reads as a static green mass.
4Fertilise consistently and thin runners as needed — liquid fertiliser dosed two to three times weekly supports active runner production and the development of full-height blades across the stand. Thin runners and daughter plants when the stand becomes denser than desired by pulling excess plants and their runner connections during water changes.
💡 Bonus Tip
Giant Hairgrass planted immediately in front of Jungle Vallisneria — Hairgrass in the midground, Jungle Val at the rear — creates a two-tier grass background that reads as genuinely naturalistic stream-edge habitat. The very fine blades of the Hairgrass in front contrast clearly with the broad ribbons of the Vallisneria behind, creating a front-to-back grass gradient with both distinct texture and height differentiation that neither plant produces alone.
🌿
Browse more aquatic plantsPair Giant Hairgrass with Vallisneria, Cryptocorynes, or Anubias for a complete planted layout. Browse our Aquatic Plants collection.
→
