Brazilian waterweed

Sold in nearly every pet shop under the name Anacharis, Egeria densa is often the first live plant a new aquarist buys. It grows fast, tolerates a wide range of water conditions, and competes with algae for nutrients — a combination that makes it genuinely useful for new and established tanks alike.

The stems are thick and covered in whorls of three to five narrow, dark green leaves that curl slightly downward. Growth is very fast under moderate light: a 15 cm stem reaches the surface in a couple of weeks and keeps growing as a floating mat if not trimmed. Regular cutting keeps it in check and produces bushy side shoots from the cut nodes.

It does well in soft or hard water and accepts a wide pH range from 5 to 9. The optimum temperature is 20 to 24 °C, but it survives from near freezing to about 30 °C, which is why it naturalises in temperate ponds as well as tropical tanks. CO₂ injection is not needed.

In many regions Egeria densa is classified as an invasive species and its sale or transport is restricted — check local regulations before buying or disposing of it. Never release it into local waterways. Disposal should be by drying or composting, not by dumping.