Photo: Lara Gudmundsdottir / CC BY-SA 4.0

Brazilian Waterweed Care

Egeria densa · Hydrocharitaceae

🐾 Pet-safe 🎯 Easy ☀️ Medium, bright indirect 💧 Every 7 days

🕮 5 min read 🕓 Last reviewed: 2026-08-23

Care at a glance

Light

Medium, bright indirect

Temperature

15–28 °C (59–82 °F)

Soil

a nutrient-rich aquarium substrate (or attached to wood/rock)

Difficulty

Easy

Mature size

20–100 cm (8–39 in)

Pet safety

Pet-safe

Care effort Medium

The short version

Beginner-friendly and forgiving.
Give it Medium, bright indirect.
Water every 7–7 days.
Safe around cats and dogs.

The Brazilian Waterweed (Egeria densa) is an aquatic plant grown submerged in freshwater aquariums. It comes from South America and is rated Easy to keep, reaching 20–100 cm. Here is how to grow it underwater — lighting, substrate, CO₂, placement and propagation.

Also known asEgeria densaアナカリス水蕴草Elodea densaÉlodée du Brésil

📋Quick facts

Growth rate	Fast
Mature size	20–100 cm (8–39 in)
Native region	South America
Plant family	Hydrocharitaceae
Toxicity	Non-toxic
Air-purifying	No
Ideal for	beginners, homes with pets, low-light rooms

⚖️Pros & cons

Pros

Non-toxic to cats and dogs
Tolerates low light
Hard to kill; great for beginners
Fast, rewarding growth

Cons

Needs high humidity to look its best

🐟Growing it in an aquarium

Keep the water at 15–28 °C. Stable, gently moving water and regular partial water changes keep it healthy; sudden swings in temperature or chemistry cause melting.

Light

Give it Medium, bright indirect-equivalent aquarium lighting. Low-tech tanks suit undemanding species; brighter light (and often CO₂) brings out the best colour and compact growth but also feeds algae, so balance it carefully.

Soil

Plant it in a nutrient-rich aquarium substrate (or attached to wood/rock). Rooted species are hungry feeders — use root tabs or a liquid aquarium fertiliser (and CO₂ for demanding types). Epiphytes like Anubias, Java fern and Bucephalandra must NOT be buried: tie or glue their rhizome to wood or rock, or they rot.

Its size and habit suit a spot in the foreground, midground or background depending on how tall it grows; trim and replant tops to keep it dense.

✂️How to propagate, step by step

Spring and early summer, during active growth, give the best success. Here is how to do it, step by step:

stem cuttings in water

Choose a healthy stem and cut a 10–15 cm piece just below a leaf node with clean, sharp scissors.
Strip the leaves off the lower third so no foliage will sit under water.
Stand the cutting in a glass of room-temperature water with at least one node submerged.
Keep it in bright, indirect light and refresh the water every few days.
When the roots are 3–5 cm long (usually 2–4 weeks), pot it into moist mix and keep it a little humid while it settles in.

🔬Classification

Plant type	Aquatic plant
Genus	Egeria
Family	Hydrocharitaceae · Hydrocharitaceae
Native to	South America

🩺Common problems

Symptom	Likely cause	What to do
Melting or dissolving leaves	Shock from a new tank (common when settling in)	Be patient — trim mushy leaves; new submerged growth usually follows.
Algae on leaves or glass	Too much light or excess nutrients in the water	Cut the lighting period, reduce feeding, and add algae-eating clean-up crew.
Leggy, sparse growth	Not enough light	Move it to brighter indirect light and pinch back to encourage bushiness.

🩺 Plant Doctor →

🐛Pests & prevention

The usual indoor pests are spider mites (fine webbing, speckled leaves), mealybugs (white cotton-wool tufts), scale (small brown bumps), and fungus gnats (tiny flies from soggy soil). Inspect any new plant before it joins the others, wipe the leaves now and then, and let the topsoil dry to keep gnats away. At the first sign, isolate the plant, wipe or rinse off what you can, and treat with insecticidal soap or neem oil every week until it is clear.

🐾Is it safe for pets?

Good news for pet owners: the Brazilian Waterweed is considered non-toxic to both cats and dogs by the ASPCA. It is one of the safer choices for homes with animals, though eating any plant can still cause mild stomach upset.

Toxicity information is a general guide based on ASPCA data. If your pet or child may have eaten any part of a plant, contact a vet or poison control right away.