Photo: Daderot / CC0

Common Eelgrass Care

Zostera marina · Zosteraceae

🐾 Pet-safe 🎯 Fussy ☀️ Full sun 💧 Every 7 days

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

Care at a glance

Light

Full sun

Temperature

2–22 °C (36–72 °F)

Soil

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

Difficulty

Fussy

Mature size

30–120 cm (12–47 in)

Pet safety

Pet-safe

Care effort High

The short version

Rewards attentive, consistent care.
Give it Full sun.
Water every 7–7 days.
Safe around cats and dogs.

The Common Eelgrass (Zostera marina) is an aquatic plant grown submerged in freshwater aquariums. It comes from Oceans and is rated Fussy to keep, reaching 30–120 cm. Here is how to grow it underwater — lighting, substrate, CO₂, placement and propagation.

Also known asZostera marinaアマモ大叶藻Hierba de marZostère marine

📋Quick facts

Growth rate	Slow
Mature size	30–120 cm (12–47 in)
Native region	Oceans
Plant family	Zosteraceae
Toxicity	Non-toxic
Air-purifying	No
Ideal for	homes with pets

⚖️Pros & cons

Pros

Non-toxic to cats and dogs

Cons

Needs high humidity to look its best
Fussy about routine and conditions
Needs a bright, sunny spot
Slow grower — patience required

🐟Growing it in an aquarium

Keep the water at 2–22 °C. Stable, gently moving water and regular partial water changes keep it healthy; sudden swings in temperature or chemistry cause melting.

Light

Give it Full sun-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:

division at repotting

Water the plant the day before to reduce stress on the roots.
Slide it out of its pot and gently shake off the loose soil.
Tease the root ball into sections, each with healthy roots and a few shoots.
Pot each section into fresh mix at its original depth.
Water them in and keep out of direct sun for a week while they recover.

seed

Sow fresh seed onto the surface of moist, fine seed-starting mix.
Cover lightly only if the seed needs darkness; most need warmth of 20–25 °C.
Keep humid under a clear cover in bright, indirect light.
Germination ranges from days to months depending on the species — be patient.
Prick seedlings out into their own small pots once they have a few true leaves.

🔬Classification

Plant type	Aquatic plant
Genus	Zostera
Family	Zosteraceae · Zosteraceae
Native to	Oceans

🩺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.
Brown spots on leaves	Inconsistent watering, cold draughts, or fungal issues	Water evenly, keep it warm, and remove badly affected leaves.

🩺 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 Common Eelgrass 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.