Photo: Alex Popovkin, Bahia, Brazil / CC BY 2.0

Monte Carlo Care

Micranthemum tweediei 'Monte Carlo' · Linderniaceae

🐾 Pet-safe 🎯 Moderate ☀️ Bright with some direct sun 💧 Every 7 days

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

Care at a glance

Light

Bright with some direct sun

Temperature

20–28 °C (68–82 °F)

Soil

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

Difficulty

Moderate

Mature size

3–5 cm (1–2 in)

Pet safety

Pet-safe

Care effort High

The short version

A little attention keeps it happy.
Give it Bright with some direct sun.
Water every 7–7 days.
Safe around cats and dogs.

The Monte Carlo (Micranthemum tweediei 'Monte Carlo') is an aquatic plant grown submerged in freshwater aquariums. It comes from Argentina and is rated Moderate to keep, reaching 3–5 cm. Here is how to grow it underwater — lighting, substrate, CO₂, placement and propagation.

Also known asMicranthemum tweediei 'Monte Carlo'モンテカルロ蒙特卡罗

📋Quick facts

Growth rate	Moderate
Mature size	3–5 cm (1–2 in)
Native region	Argentina
Plant family	Linderniaceae
Toxicity	Non-toxic
Air-purifying	No
Ideal for	homes with pets

⚖️Pros & cons

Pros

Non-toxic to cats and dogs
Compact — fits a desk or shelf

Cons

Needs high humidity to look its best
Needs a bright, sunny spot

🐟Growing it in an aquarium

Keep the water at 20–28 °C. Stable, gently moving water and regular partial water changes keep it healthy; sudden swings in temperature or chemistry cause melting.

Light

Give it Bright with some direct 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.

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	Micranthemum
Family	Linderniaceae · Linderniaceae
Native to	Argentina

🩺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 Monte Carlo 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.