Nitella flexilis Care Guide
Nitella flexilis, the smooth stonewort, is a soft, fine-branched charophyte green alga of the family Characeae that lacks the calcification of Chara.
Compiled by Aquairi from published sources · Published · Updated
Overview
Nitella flexilis, the smooth stonewort, is a charophyte green alga in the family Characeae. Unlike Chara, it lacks heavy calcium-carbonate encrustation and is soft and finely branched, forming feathery green tufts. It is a robust species that can reach about one metre in length, with branchlets in whorls that are once or twice divided. It is widely used as a model organism because of its large cell size and ease of laboratory cultivation.
Taxonomy
- Division: Charophyta
- Class: Charophyceae
- Order: Charales
- Family: Characeae
- Genus: Nitella
- Scientific name: Nitella flexilis
- Common name: Smooth stonewort
Origin
The genus Nitella was established by C. Agardh in 1824 and contains some 90 species of charophyte green algae. N. flexilis has a near-global distribution, occurring on all continents except Australia.
Habitat
It inhabits freshwater environments such as canals and other still or slow-moving waters. As a stonewort it grows submerged and anchors to the bottom, but unlike Chara it does not become calcified or stony.
Tank requirements
- Temperature: 12-24 °C (coldwater)
- pH: 6.0-8.0
- GH: 4-18 °dGH
- Lighting: medium
- CO2: not required
- Substrate: any (anchors by rhizoids)
- Maximum height: about 25 cm in aquaria
- Placement: background
Planting & care
The soft tufts anchor to the substrate and provide fine cover. The alga has a low nutrient demand and does not require CO2, and its delicate branchlets make it useful in coldwater and shrimp tanks where it offers shelter for young invertebrates.
Propagation
Propagation in cultivation is by division of established tufts.
Difficulty
The species is rated beginner-friendly. It is undemanding for light, nutrients and CO2, and tolerates a wide range of cooler water conditions.
Conservation status
IUCN Red List: Least Concern (3.1).
Propagating Nitella flexilis: Splitting the Smooth Stonewort
Overview
Nitella flexilis, the smooth or slender stonewort, is a freshwater charophyte green alga that occurs on every continent except Australia. It is robust in length, growing up to about a metre on slender axes around 1 mm wide, with branchlets in whorls divided once or twice, giving the fine, translucent, forked look that distinguishes it from the calcified Chara. It is an alga, not a vascular plant, and is anchored by rhizoids rather than true roots.
Propagation Method
Propagation is primarily vegetative through fragmentation: a separated portion of the thallus re-anchors with rhizoids and grows on. As a charophyte it also reproduces sexually via oospores, the resting zygotes typical of the Charales, which can establish new growth. Its large cells and ease of cultivation, which made it a laboratory model organism, also make fragments quick to take hold in the aquarium.
- Fragmentation / division — separate a healthy tuft gently and let it re-anchor with rhizoids.
- Oospores — sexual resting spores that can germinate into new thalli.
Step-by-Step
- Pick a healthy tuft with bright, intact, finely forked whorls.
- Tease off a portion by hand; the soft tissue tears easily, so work slowly and gently.
- Set the fragment in contact with the substrate so new rhizoids can anchor it.
- Keep it under medium light in clean, soft to moderately hard water to encourage growth.
- Leave it undisturbed until rhizoids hold and fresh feathery whorls extend.
- For sexual increase, let a mature stand fruit so oospores can seed new growth.
Conditions for Healthy Growth
Provide cool to moderate temperatures around 12–24 °C, pH about 6.0–8.0 and GH 4–18, under medium light. Unlike Chara it does not depend on heavy calcification, so it tolerates soft to moderately hard water, which suits coldwater and shrimp tanks. No added CO2 is required.
Maintenance
Keep the water clean and lighting steady, and thin the tufts when they grow dense. Because the strands are delicate, remove any torn or decaying pieces promptly so they do not break down and cloud the water. Handle the alga as little as possible to avoid shredding the fine whorls.
Common Challenges
- Fragile whorls shredding under rough handling or strong flow.
- Decaying fragments fouling the water if torn pieces are left in place.
- Smothering by debris or faster plants on its fine, soft strands.
- Confusing it with calcified Chara and pushing hard alkaline water it does not need.