Anacharis
Egeria densa
Also known asBrazilian waterweed · Elodea densa (synonym) · Egeria
Water parameters
Light and nutrients
Substrate type: any. Propagation: stem cuttings.
Substrate compatibility
| Substrate | pH effect | Nutrient load |
|---|---|---|
| Bare bottom (no substrate) (Bare bottom) | n/a | none |
| Inert sand (Pool filter sand) | neutral / inert | none |
| Inert gravel (Aquarium gravel) | neutral / inert | none |
| Limestone gravel (Crushed coral) | raises pH | none |
| Aquasoil (ADA Amazonia) | lowers pH | very high |
| Mineralized clay substrate (Seachem Fluorite) | neutral / inert | moderate |
| Dirted tank (mineralized topsoil) (DIY soil substrate) | slightly acidic | very high |
With fish
Origin and habitat
Native to warm-temperate South America, in southeastern Brazil, Argentina, Chile and Uruguay, where it grows in slow rivers, ponds, lakes and ditches. It is not a North American native; that is Elodea, with which anacharis is often confused. Egeria densa belongs to the family Hydrocharitaceae and carries the synonyms Anacharis densa and Elodea densa. Through the aquarium and pond trade it has spread to North America, Europe, Asia, Africa, Australia and New Zealand, first turning up outside its range on Long Island, New York, in 1893, and it is now a serious invasive weed in many warm regions. The plant is dioecious, and most introduced populations, including all those in the US, are male only. It grows as long, branching stems with whorls of small bright-green leaves, submersed or trailing near the surface, and is one of the most effective nutrient sponges in the hobby, pulling nitrate, phosphate and ammonia from the water.
Outdoor pond use
- USDA zones
- 5–13 (winter low around -29°C or warmer)
Care notes
Among the easiest of all aquarium plants. It grows in almost any conditions, from low to high light, with no CO2 needed, across a wide hardness range of roughly 2 to 20 GH, and it shrugs off cold, surviving down near 15°C and even under winter ice, which makes it one of the few plants suited to unheated goldfish tanks. Plant the stems or let them float; either works, and floating stems trail node roots that shelter fry and shrimp. Growth is fast under decent light, often 5–10 cm a week, so weekly trimming keeps it from taking over; cut the tops and replant to propagate. The stems are brittle and snap during maintenance, and each fragment can root and grow, part of why it is so invasive in the wild. CO2 is unnecessary but speeds and compacts growth. Its real value is functional: it competes hard with algae for dissolved nutrients and oxygenates strongly, which suits new, cycling or overstocked tanks and makes it a useful nutrient-stripping plant in aquaponics, though it is ornamental rather than edible. The main drawback is looks, since it reads as weedy next to more refined aquascape plants.