The aquarium plant commonly called “Monte Carlo” is Micranthemum tweediei ‘Monte Carlo’. It’s a popular carpeting plant in the aquascaping hobby, prized for its fresh green color and low-growing habit. Here’s a detailed description:

Appearance

• Leaves: Small, round to slightly oval leaves, bright green, about 3–5 mm wide.

• Growth pattern: Forms dense mats or carpets across the substrate when given proper conditions. Stays low (1–3 cm tall) but can grow in layered cushions.

• Stems: Fine, creeping stems that root readily into substrate, anchoring the plant as it spreads.

Habitat & Origin

• Native to Argentina (South America), making it one of the few carpeting plants not from Asia.

• Found in moist soils along riverbanks and wetlands.

Aquarium Use

• Considered an easier alternative to Hemianthus callitrichoides (Dwarf Baby Tears) because it adapts more readily.

• Popular in nature aquariums and Iwagumi layouts for its lush, lawn-like appearance.

• Works as a foreground carpet but can also grow over rocks and driftwood if attached.

Care Requirements

• Light: Medium to high light for compact growth. In low light, it grows taller and less dense.

• CO₂: Strongly recommended—while it will grow without, CO₂ ensures faster, healthier carpeting.

• Substrate: Nutrient-rich substrate helps it root and spread.

• Growth rate: Moderate; faster than Dwarf Baby Tears, slower than hairgrass.

• Maintenance: Requires trimming to prevent the carpet from lifting or shading lower layers.