Anacharis
Egeria densa
Also known asBrazilian waterweed · Elodea (misapplied) · Pond weed
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 temperate and tropical waters across the Americas, from southern Canada through the United States to Argentina. The genus Egeria (E. densa is the most common species in the trade, sometimes sold as Elodea densa) grows in slow-moving rivers, ponds, lakes, and ditches. Anacharis is one of the most widely distributed aquatic plants in the world, introduced on every continent except Antarctica for the aquarium trade, research, and as oxygenating pond plants. It forms dense, weed-like masses of long, branching stems with whorls of small bright green leaves. The plant grows both submerged and as floating stems near the surface. It's one of the most effective nutrient sponges available, rapidly absorbing nitrate, phosphate, and ammonia from the water column, which makes it popular for new tank cycling, goldfish tanks, and overstocked community tanks.
Outdoor pond use
- USDA zones
- 5–13 (winter low around -29°C or warmer)
Care notes
Among the easiest aquarium plants. Grows in virtually any conditions: low to high light, no CO2, soft or hard water (actually prefers harder water, GH 8+), and a wide temperature range (15–28°C). The cold tolerance makes it one of the few aquarium plants suitable for unheated goldfish tanks. Plant stems in the substrate or let them float; the plant grows either way. Floating stems produce a tangle of roots from the nodes that serves as fry cover and shrimp habitat. Growth is fast under moderate to high light; weekly trimming is necessary to prevent it from taking over the tank. Cut tops and replant to propagate. The stems are brittle and break easily during maintenance, creating fragments that each grow into new plants, which is part of why it's so invasive in the wild. In hard water with good light, the stems can grow 5–10 cm per week. In low-tech setups, it's slower but still reliable. Nutrient demands are moderate; it pulls what it needs from the water column. Anacharis competes with algae for dissolved nutrients, which is one of its most useful qualities in new or unbalanced tanks. The main downside is aesthetic: it looks somewhat weedy and monotonous compared to more refined planted tank species. Many keepers use it as a functional plant (nutrient export, fry cover) rather than a design element.