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Canadian Waterweed
Elodea canadensis
Hydrocharitaceae
📍 North America (Canada and the northern United States)
Elodea canadensis is a submerged, fast-growing stem plant with whorls of small, dark green, lance-shaped leaves arranged in groups of three along long, branching stems, giving it a dense, bushy appearance ideal for background planting and providing refuge for fish and fry. It is an excellent oxygenator and nutrient absorber, making it a practical choice for low-tech, cold-water, and temperate aquariums. WARNING: Elodea canadensis is a highly invasive species outside its native range — it must never be released into natural waterways, ponds, or the wild, as it can devastate native aquatic ecosystems.
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Compatible Livestock
Shares the same cool-water temperature range; uses dense stems for shelter and spawning
Tolerates similar cool temperatures; may nibble occasionally but generally leaves the plant intact
Thrives in the same cool, well-oxygenated conditions that Elodea helps create
Will graze on dying or decaying leaves, helping keep the plant tidy without damaging healthy growth
Common Diseases
Yellowing and Leaf Loss
Leaves turn pale yellow or transparent and drop from the stem, often starting at the base of the plant
Usually caused by insufficient light or nutrient deficiency; increase photoperiod or intensity, and consider adding a liquid fertilizer with iron and micronutrients
Algae Overgrowth on Leaves
Green, brown, or black algae coating the leaf surfaces, blocking light and causing dieback
Reduce excess nutrients and light duration; improve water circulation; introduce algae-grazing snails or shrimp; manually remove heavily affected stems
Stem Rot
Stems become soft, brown, and mushy, particularly at the base or where the plant is buried in substrate
Trim affected sections immediately; replant healthy top cuttings; improve water flow and avoid burying stems too deeply in anaerobic substrate
Melting in Warm Water
Rapid deterioration of leaves and stems, turning translucent and disintegrating when water temperature exceeds 24 C (75 F)
Elodea is a cool-water species and will decline in tropical temperatures; lower tank temperature to the appropriate range or replace with a warm-water tolerant alternative
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Quick Facts
- co2
- Not required
- light
- Low to Medium (15-50 PAR); tolerates a wide range
- placement
- Background; grown rooted in substrate or left floating as a nutrient-absorbing mass
- substrate
- Any substrate or none; roots anchor but nutrients are primarily absorbed through the water column
- growth rate
- Fast
- propagation
- Stem cuttings; simply cut and replant or float; also spreads via fragmentation naturally
Water it likes
- ph
- 6.5-8.0
- hardness
- 5-20 dGH
- temperature
- 50–72°F (10–22°C)
Legality
No state or federal restrictions on record for this species.
Not legal advice, and possibly incomplete or out of date. Rules vary by state and locality and change over time — always confirm the current regulations with your state wildlife or agriculture agency before buying, keeping, or shipping this species.