Fact sheet
- Family
- Cyperaceae (sedges)
- Origin
- Wetlands and shorelines across much of the Northern Hemisphere
- Height
- 2–4 in (5–10 cm) for E. parvula, 4–8 in (10–20 cm) for E. acicularis
- Light
- Medium to high
- CO2
- Strongly recommended for a carpet
- Growth rate
- Moderate, spreads by runners
- Difficulty
- Moderate
- Placement
- Foreground carpet, edges of rock and wood
- Temperature
- 68–82 °F (20–28 °C)
- pH
- 6.0–7.5
01
Dwarf hairgrass at a glance
Dwarf hairgrass is a small sedge with thin, needle-like green blades that grow from a network of runners in the substrate. Once established, it forms a lawn that sways gently in the current, which is why it is the go-to foreground plant for Iwagumi aquascapes and nature-style layouts.
Two plants are sold under the name. Eleocharis parvula stays short and fine, around 2–4 inches. Eleocharis acicularis, sometimes labeled as hairgrass or needle spikerush, grows taller and looser, often 4–8 inches, while its 'Mini' cultivar stays very short. Labels are not always reliable, so judge by the plant you receive and trim accordingly. Both need the same care.
- Creates a natural grass carpet that other carpeting plants cannot imitate
- Tolerates a wide temperature range, including cooler, unheated tanks
- Spreads quickly with CO2 and good light, slowly without
- Needs regular trimming and a clean foreground to stay tidy
02
Dwarf hairgrass carpet: what it needs to succeed
A dense dwarf hairgrass carpet depends on three things working together: substrate, light and CO2. If one is missing, the plant survives but spreads slowly, and algae often move in first.
Substrate comes first. Runners need a fine-grained, soft substrate they can push through, and the roots take nutrients from it. An aquarium soil (aquasoil) is the easiest option; fine sand or small gravel works if you add root tabs. Our guide to the best aquarium substrate compares nutrient-rich soils and inert options.
Light should be medium to high at the substrate level, not just near the surface. In tall tanks, a weak light leaves the foreground in shade and the carpet thins out. See our picks for the best aquarium light if you are upgrading.
CO2 is technically optional, and hairgrass does grow in low-tech tanks. But injected CO2 is the single biggest factor in how fast and how evenly it carpets. Read our guide to aquarium CO2 for the basics, and our review of the best aquarium CO2 system when you are ready to buy.
| Setup | Expected result |
|---|---|
| Aquasoil + strong light + injected CO2 | Dense carpet in about 6–10 weeks |
| Aquasoil + medium light, no CO2 | Patchy carpet over several months |
| Inert gravel + low light, no CO2 | Survives as sparse tufts, slow spread |
| Dry start, then flooded with CO2 | Carpet often established before flooding |
03
How to plant dwarf hairgrass
Most hairgrass comes in pots or in-vitro cups. Splitting it into many small plugs is what makes the carpet close quickly: one pot can cover a good part of a 10-gallon foreground.
- Remove the plant from the pot and rinse away all rock wool, or rinse the gel from in-vitro cups.
- Trim the roots to about half an inch (1 cm) and the blades to 1–2 inches (3–5 cm).
- Divide the mass into small clumps of 5–10 blades each.
- With planting tweezers, push each clump about half an inch (1–1.5 cm) into the substrate at a slight angle.
- Space the clumps about 1 inch (2–3 cm) apart in a grid; closer spacing means a faster carpet.
- Fill the tank slowly over a plate or bag so the water does not uproot the plugs.
Dry start method: plant the plugs in moist substrate, cover the tank with plastic wrap and keep the light on 8–10 hours a day for 4–6 weeks without water. Hairgrass roots and spreads without algae competition. Flood carefully afterwards and make sure the tank is cycled before adding fish.
04
Care, trimming and propagation
Hairgrass propagates itself: each clump sends out runners a few centimeters under the surface, and new plantlets appear along them. Encourage this with steady light, CO2 and nutrients. A complete liquid fertilizer plus a root tab under the carpet every few months works in most tanks; our page on aquarium fertilizer explains the options.
Trim regularly once the carpet is established. Cut the blades back to about 1 inch (2–3 cm) with curved aquascaping scissors every 2–4 weeks. Trimming makes the carpet thicker and shorter, and stops older blades from shading new shoots. Siphon the clippings out afterwards, because they decay quickly.
Clean the foreground gently. A dense carpet traps fish waste and uneaten food. Hover a gravel vacuum just above the blades during water changes rather than digging into the substrate. To propagate for another tank, simply lift a clump with roots from the edge of the carpet and replant it.
05
Common dwarf hairgrass problems
Most issues appear in the first weeks or when the carpet becomes too thick.
| Symptom | Likely cause | What to do |
|---|---|---|
| Blades turn brown after planting | Adaptation from emersed to submerged growth | Wait 2–4 weeks; trim dead blades, new green shoots follow |
| Yellow or pale blades | Low nutrients, iron shortage or not enough CO2 | Check fertilizer and CO2, add root tabs |
| No new runners after a month | Light too weak at the bottom, inert or coarse substrate | Increase light, add root tabs or switch to aquasoil |
| Hair algae or black tufts in the carpet | Unstable CO2, excess light, debris | Trim affected areas, stabilize CO2, see black beard algae |
| Carpet lifts or rots at the base | Very thick old carpet trapping gas and debris | Thin out sections and replant fresh plugs |
Bottom-digging fish such as large cichlids or goldfish uproot new plugs. Algae eaters like Amano shrimp and otocinclus are good partners, as long as the carpet is well rooted.
06
Tank ideas with dwarf hairgrass
The classic use is a rock-only Iwagumi with a hairgrass lawn around the stones and a school of small fish such as rasboras. It also works as a soft edge between a Monte Carlo foreground and taller background plants, or as a grassy border in a nano shrimp tank, where cherry shrimp graze between the blades. Compare it with other options in our guide to carpet aquarium plants before you decide.
Frequently asked questions
Frequently asked questions
How long does it take for dwarf hairgrass to carpet?
With aquasoil, strong light and injected CO2, a dwarf hairgrass carpet usually closes in 6–10 weeks when plugs are planted about an inch apart. Without CO2 and with moderate light, expect several months and a patchier result. A dry start of 4–6 weeks before flooding can shorten the wait.
Can dwarf hairgrass grow without CO2?
Yes, it survives and grows slowly in low-tech tanks, especially with an aquarium soil and good light. The difference is speed and density: without CO2 it tends to form sparse tufts rather than a thick lawn, and algae have more time to settle. Liquid carbon products are not a full replacement for CO2.
What is the difference between Eleocharis parvula and acicularis?
Eleocharis parvula is shorter and finer, usually 2–4 inches, and is often the plant aquascapers want for a low lawn. Eleocharis acicularis grows taller and looser, often 4–8 inches, though its 'Mini' form stays very short. Care is the same; the main difference is how often you need to trim.
Why is my dwarf hairgrass turning brown?
Browning in the first weeks is normal: most hairgrass is grown out of water and the old blades die back while new submerged ones grow. Trim the brown parts and keep conditions stable. If browning continues after a month, check light at the bottom, CO2 and nutrients, especially iron.
How do you trim dwarf hairgrass?
Use curved aquascaping scissors and cut the blades back to about one inch every 2–4 weeks, working in small sections across the carpet. Regular trimming keeps the lawn short and encourages new runners. Remove the clippings with a net or siphon right away, since they rot quickly.
Sources and references
Written and reviewed by the handsoffmyhobby editorial team according to our editorial policy.
