Pygmy chain sword
A small grass-like runner plant used as an undemanding carpet in medium light.
Requirements
- Scientific name
- Helanthium tenellum
- Family
- Alismataceae
- Light
- Medium
- CO₂
- Beneficial
- Nutrients
- moderate
- Growth rate
- Moderate
- Placement
- Foreground
- Feeding
- root feeder
- Temperature
- 20–28 °C
- pH
- 6–7.8
- Hardness
- 2–15 °dGH
- Height
- 3–10 cm
Identity
- Common name
- Pygmy chain sword
- Scientific name
- Helanthium tenellum
- Family
- Alismataceae
- Synonyms
- Echinodorus tenellus
How to plant it
The commonest way to kill an aquarium plant is to install it wrongly. This is the first thing to get right.
Roots buried, crown above the substrate
Nutrition reaches this plant mainly through its roots, so root tabs matter more than liquid dosing in an inert substrate.
Growing conditions
| Input | Requirement | Notes |
|---|---|---|
| Light | Medium | Match plants to the light you have rather than raising light to suit the plant — that grows algae. |
| CO₂ | Beneficial | Not a requirement, though growth is faster with it. |
| Nutrients | moderate | Use root tabs in inert substrate. |
| Temperature | 20–28 °C | |
| pH | 6–7.8 | |
| Hardness | 2–15 °dGH | |
| Growth rate | Moderate |
Propagation
Spreads by runners.
Emersed growth and melting
Commercially grown out of water. Expect the emersed leaves to die back after planting while new submersed-form leaves grow from the crown. This is a conversion, not a disease.
Common problems
- carpet thins in low light
- melt on conversion
Work from the observation: melting, yellow leaves, holes in leaves and poor growth.
Fish and invertebrate compatibility
- Resists grazing
- moderate
- Resists digging
- poor
Evidence
| Claim | Value | Evidence type | Confidence | Source |
|---|---|---|---|---|
| scientific name | Helanthium tenellum | Observed / measured | high confidence | Plants of the World Online |
| temperature | 20–28 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| light requirement | medium | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| co2 requirement | beneficial | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| growth rate | moderate | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| placement | foreground | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 6–7.8 pH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| general hardness | 2–15 °dGH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| height | 3–10 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
Why we say this
What each figure on this page rests on, and how far that is from being independently established.
Every figure on this page has a provenance. Open any claim to see what AquariumHQ holds for it, which sources say what, and what a claim of that kind actually needs. Different claims need different evidence: an accepted scientific name is settled by one authority, while a legal restriction needs a current primary instrument. A single source is often the right answer rather than a thin one. Light and CO2 categories are aquarium conventions rather than measurements, and are labelled as such — AquariumHQ has taken no PAR readings and does not publish figures it has not taken.
scientific nameOne sourceBased on a verified authoritative source.1 citation, 1 independent origin
Checked against gbif on 2026-08-11 and confirmed accepted.
What this kind of claim needs: accepted botanical name — 1 authoritative source in an appropriate context. Checked against gbif on 2026-08-11. One botanical authority is what this class requires.
What would improve this: Corroborate against a second, independent source.
temperatureAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: how to grow the plant — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
light requirementAquariumHQ's judgement — no authority publishes thisAquariumHQ's own position, derived from evidenced inputs.
No external authority publishes this. The rationale carries the reasoning.
What this kind of claim needs: how to grow the plant — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Keep the rationale current. There is no source to find.
co2 requirementAquariumHQ's judgement — no authority publishes thisAquariumHQ's own position, derived from evidenced inputs.
No external authority publishes this. The rationale carries the reasoning.
What this kind of claim needs: how to grow the plant — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Keep the rationale current. There is no source to find.
growth rateAquariumHQ's judgement — no authority publishes thisAquariumHQ's own position, derived from evidenced inputs.
No external authority publishes this. The rationale carries the reasoning.
What this kind of claim needs: how to grow the plant — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Keep the rationale current. There is no source to find.
placementAquariumHQ's judgement — no authority publishes thisAquariumHQ's own position, derived from evidenced inputs.
No external authority publishes this. The rationale carries the reasoning.
What this kind of claim needs: how to grow the plant — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Keep the rationale current. There is no source to find.
phAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: how to grow the plant — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
general hardnessAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: how to grow the plant — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
heightAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: size a well-kept specimen reaches — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.