Elodea densa
A fast-growing cool-water stem plant sold everywhere as pond oxygenator and aquarium filler.
Requirements
- Scientific name
- Egeria densa
- Family
- Hydrocharitaceae
- Light
- Medium
- CO₂
- Not required
- Nutrients
- moderate
- Growth rate
- Very fast
- Placement
- Background
- Feeding
- both
- Temperature
- 10–25 °C
- pH
- 6.5–8.5
- Hardness
- 3–25 °dGH
- Height
- 30–100 cm
Identity
- Common name
- Elodea densa
- Scientific name
- Egeria densa
- Family
- Hydrocharitaceae
- Also sold as
- egeria, anacharis, pondweed
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 both roots and leaves, so either route works.
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 | Not required | Not a requirement, though growth is faster with it. |
| Nutrients | moderate | Dose a complete liquid fertiliser. |
| Temperature | 10–25 °C | |
| pH | 6.5–8.5 | |
| Hardness | 3–25 °dGH | |
| Growth rate | Very fast |
Propagation
Cuttings root readily.
Common problems
- melts in warm water
- brittle stems
- outgrows tank
Work from the observation: melting, yellow leaves, holes in leaves and poor growth.
Fish and invertebrate compatibility
- Resists grazing
- poor
- Resists digging
- moderate
Worth knowing
- Struggles above about 25 °C, which makes it a poor fit for most tropical community tanks.
Legal status and responsible disposal
Restriction note
Egeria densa is listed as an invasive alien species of Union concern in the EU, where keeping, sale and transport are prohibited. It is also restricted in several other countries. Check your jurisdiction before acquiring it.
Never release aquarium life into the wild
Aquarium animals, plants, and aquarium water must never be released into ponds, rivers, canals, drains or the sea — not even in a country where the species is sold freely. Released fish and invertebrates establish populations that displace native species, and released plants and water carry pathogens, parasites and fragments capable of spreading without any animal at all. If you can no longer keep an animal, rehome it through an aquarium society, a retailer that accepts returns, or another keeper.
Evidence
| Claim | Value | Evidence type | Confidence | Source |
|---|---|---|---|---|
| scientific name | Egeria densa | Observed / measured | high confidence | Plants of the World Online |
| temperature | 10–25 °C | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| light requirement | medium | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| co2 requirement | not-required | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| growth rate | very-fast | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| placement | background | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| ph | 6.5–8.5 pH | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| general hardness | 3–25 °dGH | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| height | 30–100 cm | Aquarium-literature consensus | high 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 nameSources disagreeWe do not have a basis for this and say so.1 citation, 1 independent origin
Authorities disagree. gbif accepts "Elodea densa"; the catalogue keeps "Egeria densa" and records the disagreement rather than taking a side.
What this kind of claim needs: accepted botanical name — 1 authoritative source in an appropriate context. Authorities disagree: gbif accepts "Elodea densa" and the catalogue keeps "Egeria densa". Recorded rather than resolved.
What would improve this: Editorial resolution. More reading will not settle this on its own.
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.