Micranthemum umbrosum

Micranthemum umbrosum is native to the eastern United States and Central America, where it inhabits shallow, slow-moving water bodies, stream margins, and seasonally flooded ditches. In the aquarium it produces incredibly dense masses of small, round, bright-green leaves that can be shaped into a carpet, midground fill, or floating mat depending on conditions and how the aquarist manages its growth. It is often confused with or compared to Hemianthus callitrichoides Cuba, but M. umbrosum has noticeably larger leaves and a more forgiving cultivation profile that makes it suitable for intermediate hobbyists. Unlike HC Cuba, it does not require extreme light intensity at substrate level to form a flat carpet — it will carpet at moderate lighting levels with CO2, though it also grows upright without carpeting under low light. The plant's rapid growth rate makes it effective for nutrient export and algae prevention in the early stages of a new aquascape. Its lush, fine-textured appearance provides beautiful scale contrast alongside larger-leaved plants and hardscape.

Placement Plant in the foreground for carpeting use, or allow to grow as a low-midground fill plant. Anchoring small portions near hardscape creates a natural, overgrown look around stones and wood.

Lighting Moderate-to-high lighting (40–75 PAR at substrate) produces the best carpet. It tolerates lower light better than Glossostigma but becomes upright and bushy rather than a flat mat. Ensure the substrate zone receives adequate light.

CO2 & Fertilisation CO2 injection at 15–25 ppm accelerates carpeting growth. A complete fertiliser programme including macro and micro nutrients applied weekly is beneficial. Nutrient-rich substrate helps the plant thrive as a carpet.

Propagation Stem cuttings pressed into substrate root quickly. Portions of the carpet can be dug up and replanted elsewhere. Fast propagation makes it easy to fill a tank foreground within a few weeks.

Trimming Trim every 2–4 weeks with curved scissors. Cut to 2–3 cm for a carpet effect or allow taller growth for a bushy midground appearance. Remove trimmed material carefully to prevent decomposing debris from fouling the water.