Fact sheet
- Common names
- Monte Carlo, Micranthemum Monte Carlo, New Large Pearl Grass
- Family
- Linderniaceae
- Origin
- Argentina (collected near Monte Carlo, Misiones)
- Height
- 0.8–2 in (2–5 cm)
- Light
- Medium to high
- CO2
- Strongly recommended, optional under medium light
- Growth rate
- Medium to fast
- Difficulty
- Medium
- Placement
- Foreground carpet
- Temperature
- 68–82 °F (20–28 °C)
- pH
- 6.0–7.5
01
Monte Carlo aquarium plant overview
Monte Carlo is a creeping stem plant from Argentina that the Danish nursery Tropica brought into the trade in the early 2010s. It spreads by runners that root as they go, producing a low mat of round, bright green leaves. In the aquarium it is mostly used as a Monte Carlo carpet in the foreground, and it has become a popular, more forgiving alternative to HC Cuba (Hemianthus callitrichoides).
Compared with other carpeting aquarium plants, Monte Carlo has larger leaves, roots more readily and tolerates slightly less light. It is still not a true low-tech plant: without enough light it grows upward instead of across, and without good nutrition the lower layers yellow. If you want a carpet in a tank without CO2, read the section on low-tech setups before you buy.
02
What Monte Carlo needs: light, CO2 and substrate
Light is the first factor. Medium to high light, roughly what a good planted-tank LED delivers over a 12–16 in (30–40 cm) deep tank, keeps the plant compact and creeping. Under weak light the stems stretch toward the surface and the carpet thins out. Our aquarium light buying guide lists fixtures with enough output for carpets.
CO2 makes the biggest difference to speed and density. With injected CO2 at about 20–30 ppm, Monte Carlo can cover the foreground within two months. Without it, the plant can still grow under medium light, but slowly, and it is more prone to algae on the leaves. Our complete guide to aquarium CO2 explains how to set up and tune a system.
Substrate matters because Monte Carlo has fine roots that feed heavily from the bottom. An aqua soil or a nutrient-rich layer under fine gravel gives the best results. Coarse gravel makes the small portions float away. See our aquarium substrate reviews for soils that suit carpet plants.
| Setup | Light | CO2 | Expected result |
|---|---|---|---|
| High-tech | Medium to high | 20–30 ppm | Dense carpet in 6–10 weeks |
| Medium | Medium | Liquid carbon or low CO2 | Patchy carpet in 3–4 months |
| Low-tech | Low to medium | None | Slow, taller growth, risk of thinning |
03
How to plant Monte Carlo
Most hobbyists buy Monte Carlo as tissue culture in small cups. These plants are pest-free and snail-free, but they were grown emersed (out of water) and will adapt their leaves once submerged.
- Rinse the gel out of the tissue culture cup under lukewarm water.
- Tear or cut the mass into small portions about the size of a fingertip, each with a few roots.
- Wet the substrate and lower the water level, or plant before filling the tank.
- Push each portion 0.4–0.8 in (1–2 cm) deep with long planting tweezers, at an angle so the leaves rest on the surface.
- Space portions 1–2 in (2–5 cm) apart. Closer spacing fills faster.
- Fill the tank slowly over a plate or bag so the water stream does not uproot the clumps.
The dry start method works very well with Monte Carlo: plant into a moist substrate, cover the tank with cling film, keep the lights on and mist daily for 3–6 weeks until the roots anchor, then flood slowly.
04
Daily and weekly care
Once rooted, Monte Carlo is fairly undemanding as long as nutrients stay balanced. Keep a regular schedule of aquarium fertilizer: an all-in-one liquid for the water column, plus root tabs under the carpet once an inert substrate or an older soil runs low. Iron and potassium deficiencies show quickly as pale new leaves or pinholes.
Trim the carpet every 2–4 weeks once it closes. Use curved scissors and cut it back to a thin layer, about 0.4 in (1 cm). If the mat gets too thick, the lower leaves lose light and water flow, rot, and the whole carpet can lift off the substrate. After a heavy trim, siphon the clippings out during your weekly water change.
Good flow across the foreground keeps debris from settling on the leaves. In high-tech tanks, aim for a weekly 30–50% water change for the first month, while the soil releases ammonia and the plant adapts.
05
Propagation
Monte Carlo propagates itself through runners, so a healthy carpet keeps expanding without help. To fill gaps or start a new tank, lift a section of carpet with its roots, split it into small portions and replant them the same way as tissue culture. Trimmings without roots can also be pressed back into the substrate, though they take longer to anchor.
For your own tanks, splitting a healthy patch is the cheapest way to cover a large foreground. Replant the new portions in a part of the tank with good light and flow, and they usually start sending out runners within two to three weeks.
06
Common Monte Carlo problems
Most problems come from the transition after planting, from weak light or from an unbalanced nutrient and CO2 regime.
| Symptom | Likely cause | Fix |
|---|---|---|
| Leaves melt in the first weeks | Adapting from emersed to submersed growth | Leave the roots in place, remove dead leaves, new growth follows |
| Portions float up | Planted too shallow, coarse substrate, fish digging | Replant deeper, use soil or fine sand, try a dry start |
| Stems grow upward, gaps between leaves | Light too weak or too far away | Increase intensity or photoperiod moderately |
| Yellow new leaves | Iron or general nutrient shortage | Add a complete liquid fertilizer and root tabs |
| Carpet lifts or rots underneath | Mat too thick, poor flow | Trim hard to 1 cm, improve circulation |
| Algae on the carpet | Light too strong for available CO2 and nutrients | Shorten the photoperiod, balance CO2, clean regularly |
Hair algae and black beard algae are hard to remove from a carpet. Fix the CO2 and light balance early rather than trying to clean individual leaves later.
07
Can you grow Monte Carlo without CO2?
Yes, with patience. In a low-tech tank, give medium light for 7–8 hours a day, a rich substrate, and dose a liquid carbon product as a supplement. Plant more densely, since growth is slow. The carpet will be looser and taller than in a CO2 tank, and some keepers find that it thins out after a few months. If you are still choosing a foreground plant, compare it with dwarf hairgrass, a grassy carpet with similar light needs, before deciding which look suits your scape.
For truly undemanding plants, start with our list of the best aquarium plants for beginners.
08
Tank ideas with Monte Carlo
Monte Carlo is a natural fit for an Iwagumi aquascape, where a single carpet plant surrounds a group of stones. It also works in nature-style layouts as a soft foreground in front of stem plants, and in nano tanks where its small leaves keep the scale realistic.
Small, peaceful fish look best over a carpet: ember tetras, celestial pearl danios or a group of cherry shrimp, which graze biofilm between the leaves without damaging the plant. Avoid goldfish, large cichlids and any digging bottom fish, which uproot the carpet before it can anchor.
Frequently asked questions
Frequently asked questions
Is Monte Carlo a good aquarium carpet plant for beginners?
It is one of the easier carpet plants, but not a beginner plant in the same way as java fern or anubias. Monte Carlo needs medium to high light, a nutrient-rich substrate and ideally CO2. If those three are in place, it roots readily and spreads faster than HC Cuba, which makes it a good first carpet.
Why is my Monte Carlo floating?
Floating portions are usually planted too shallow, in coarse gravel, or are uprooted by fish and by water flow before the roots anchor. Replant small portions 1–2 cm deep with tweezers, use aqua soil or fine sand, and consider a dry start so roots develop before the tank is flooded.
How fast does Monte Carlo spread?
With strong light, injected CO2 and good fertilization, Monte Carlo usually covers the foreground in about 6–10 weeks when planted 2–5 cm apart. Without CO2, growth is much slower and can take several months, and the carpet stays looser. Wider spacing also adds a few weeks.
What is the difference between Monte Carlo and HC Cuba?
Both are Micranthemum-type carpet plants, but HC Cuba (Hemianthus callitrichoides) has tiny leaves of about 2 mm and needs very high light and CO2. Monte Carlo has larger, rounder leaves of around 3–5 mm, roots more easily and tolerates more moderate conditions, so it is often used as an HC alternative.
Is Monte Carlo safe with shrimp?
Yes. Shrimp do not eat healthy Monte Carlo and actually help by grazing biofilm and algae between the leaves. Just make sure any fertilizer you dose is labelled shrimp-safe and follow the dose on the bottle, especially in small tanks.
Sources and references
Written and reviewed by the handsoffmyhobby editorial team according to our editorial policy.
