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PlanteasyFreshwater

Curly Waterweed

Lagarosiphon major

Hydrocharitaceae

📍 Native to southern Africa (South Africa, Zimbabwe, Lesotho); invasive in Europe, New Zealand, Australia, and parts of North America

Lagarosiphon major is a vigorous, submerged oxygenating plant featuring long, spirally recurved dark green leaves densely arranged along brittle, branching stems, giving it a distinctive curly, bottle-brush appearance. In aquascapes it is used as a fast-growing background or mid-tank oxygenator, particularly suited to cold-water and temperate setups. WARNING: This species is a highly invasive aquatic weed banned in several countries — it must never be released into natural waterways, ponds, or the wild, as it can devastate native aquatic ecosystems.

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Common Diseases

Stem Rot

Symptoms

Soft, brown, mushy sections along the stem, often starting at the base or where stems are buried too deeply

Treatment

Remove affected sections, trim to healthy tissue, replant cuttings in well-oxygenated water, and improve water circulation

Algae Overgrowth (Hair/Thread Algae)

Symptoms

Fine green threads tangling around leaves and stems, reducing light penetration and smothering growth

Treatment

Manually remove algae, reduce photoperiod, ensure adequate water flow, and introduce algae-grazing species such as Amano shrimp if temperature permits

Nutrient Deficiency (Iron/Micronutrients)

Symptoms

Yellowing or pale new growth, stunted shoot tips, loss of deep green coloration

Treatment

Dose a balanced liquid micronutrient fertiliser with iron; ensure adequate lighting to support uptake

Excessive Fragmentation

Symptoms

Brittle stems breaking apart easily, scattering fragments throughout the tank

Treatment

Handle plants gently during maintenance, use fine-mesh nets when performing water changes, and remove all fragments promptly to prevent uncontrolled spread within the aquarium

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Quick Facts

co2
Not required
light
Medium to High (30-60+ PAR); tolerates lower light but growth slows significantly
placement
Background to midground; grown rooted in substrate or left floating as a loose oxygenator
substrate
Adaptable; grows in gravel, sand, or plain substrate — nutrients absorbed primarily through the water column
growth rate
Fast
propagation
Stem cuttings; simply cut and replant or float — even small fragments can root and establish new plants

Water it likes

ph
6.5-8.5
hardness
5-20 dGH
temperature
41–72°F (5–22°C)

Legality

No state or federal restrictions on record for this species.

Not legal advice, and possibly incomplete or out of date. Rules vary by state and locality and change over time — always confirm the current regulations with your state wildlife or agriculture agency before buying, keeping, or shipping this species.

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