PlantFreshwaterIntermediate
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Eleocharis sp. "montevidensis"
Eleocharis sp. "montevidensis"
A tall, erect grass native to the shallow marshes of South America. Ideal for background placement, it demands medium to strong lighting to maintain elegant growth.
Water Temperature
18 - 27 °C
pH Value
5.5 - 7
Water type
Freshwater
Light
Medium - High
CO2
Medium - High
Expected height
55 cm
Expected width
20 cm
GH
0 - 20 dGH
KH
0 - 14 dKH
Species description
Geographical Origin and Habitat: Native to South America, particularly the regions around Uruguay and Argentina. It grows in shallow marshy waters, sandy swamps, and riverbanks subject to seasonal flooding.
Taxonomy & Genetics: Belongs to the Cyperaceae family, genus Eleocharis. The species montevidensis is known to be one of the tallest and most robust hairgrass variants commercially available.
Physical Structure: Characterized by vertical cylindrical stems, hollow inside, growing densely from a creeping rhizome. It can exceed 50-60 cm in height, bending gracefully over the water surface.
Color & Texture: It features a uniform dark green coloration. The smooth and thin stems create a dense vertical texture reminiscent of wild natural reed beds.
Care, breeding and tankmates
Lighting & CO2: Requires medium to strong lighting to grow erect. CO2 is not strictly mandatory but accelerates growth and improves clump density.
Nutrition & Substrate: A fertile substrate or the use of root tabs is very useful to support the development of the underground rhizome.
Water Chemistry: Tolerant regarding water chemistry; ideal pH between 6.0 and 7.5. Prefers soft to medium water hardness (KH 2-12) and temperature between 15 and 28 °C.
Space Management & Placement: Should be placed exclusively in the background or along the sides of the aquarium. It is ideal for hiding filters or heaters.
Pruning: Pruned by trimming the stems to the desired length. If it grows too large, it is recommended to thin out the clump by removing the oldest stems at the base.
Risks & Diseases: Can be subject to yellowing if iron is lacking in the substrate. Filamentous algae can cling to the stems if water circulation is poor.
Geographic Origin and Distribution
Native to South America, particularly the regions around Uruguay and Argentina. It grows in shallow marshy waters, sandy swamps, and riverbanks subject to seasonal flooding.
Origin
Extra-Amazon South America
Plant profile
- Placement
- Midground
- Because of its potential to reach the water surface, it is best placed in the background of the aquarium. It can be planted in dense clusters to hide aquarium equipment such as heaters or filter intakes. In taller aquariums, it creates a striking vertical accent. It should be given enough space so it does not overshadow shorter foreground species.
- Botanical form
- Rhizome
- Eleocharis sp. 'montevidensis' features long, elegant stems or leaves that grow vertically towards the light source. It can form dense thickets that provide excellent hiding spots for fish and fry. The leaves are typically bright green, adding a vibrant splash of color. Its structure is quite flexible, allowing it to sway beautifully in strong water currents.
- Growth
- Medium
- This plant exhibits a rapid growth rate, often reaching the water surface within a matter of weeks. The growth can be accelerated even further with intense lighting and CO2. Its fast growth makes it an excellent candidate for newly set up tanks to combat algae. Frequent trimming will be required to keep it from taking over the tank.
- Substrate
- High
- Eleocharis sp. "montevidensis", known as Giant Hairgrass, requires a robust and nutrient-rich substrate to support its remarkably tall, needle-like growth. Due to its size, it develops a deep and extensive root system that demands a substrate depth of at least 5-7 centimeters for secure anchoring. A fertile aquatic soil is crucial, as this species draws significant amounts of minerals directly from its root base to fuel vertical growth. While a fine-grained substrate is preferred, it can tolerate slightly coarser gravels provided that root tabs or base fertilizers are abundant.
- Column fertilization
- Recommended
- Liquid fertilization is very effective for this species, as it readily absorbs nutrients through its leaves. A balanced liquid fertilizer containing both macros and trace elements should be dosed regularly. Potassium and iron are particularly important to maintain strong stems and vibrant leaf color. Without sufficient water column nutrients, lower leaves may begin to degrade.
- Root fertilization
- None
- While it draws heavily from the water column, a nutrient-rich substrate will produce the most robust specimens. Root tabs placed near the base can provide a secondary nutrient source and anchor the plant securely. A good substrate helps prevent the stems from rotting at the base. However, it can still grow reasonably well in inert substrates with adequate liquid dosing.
- Trimming
- Occasional
- Regular pruning is necessary to manage its height and encourage lateral branching. You can simply cut the upper portion of the plant and replant the healthy tops to increase the density of the group. If the plant reaches the surface, it may bend and shade other plants, so timely trimming is crucial. Discard any old or decaying lower stems during maintenance.
- Propagation
- Cuttings
- Propagation is straightforward and usually achieved through cuttings or division, depending on its specific morphology. If it produces runners or side shoots, these can be separated once they have developed roots. Replanting top cuttings is the easiest way to multiply stem-like growth. It is a highly prolific plant under the right conditions.
- Sensitivity
- Moderate
- It is generally a very resilient plant, adaptable to a wide range of water parameters. However, sudden changes in water chemistry or temperature can sometimes cause melting. It requires adequate light reaching the lower portions; otherwise, it may drop its bottom leaves. It is mostly unaffected by typical aquarium medications.
- Layout role
- Midground, Background
- This plant excels as a background filler, providing a tall, green curtain that adds depth and volume. It contrasts well with red plants or broad-leaved species in the midground. Its vertical lines can help draw the eye upwards, enhancing the sense of scale in the aquascape. It is also highly useful in breeding tanks for fish that require dense cover.
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
