Pearlweed Aquarium Care Guide: Micranthemum Micranthemoides
Few stem plants are as forgiving and as photogenic as pearlweed — a bright lime carpet former that delivers oxygen pearling so visibly it gave the species its name. Pearlweed aquarium setups suit beginners stepping up from low-tech basics into their first carbon-injected scape. This care guide from Gensou Aquascaping at 5 Everton Park covers Micranthemum micranthemoides specifics, propagation cadence, and the parameters that turn it from a leggy stem into a dense midground feature.
Plant Identification
Micranthemum micranthemoides, commonly called pearlweed or baby tears (not to be confused with HC Cuba), produces small rounded leaves in opposing pairs along a thin stem. Mature stems reach 10-15 cm vertically before naturally branching. Colour ranges from spring green under low light to bright lime under high-PAR fixtures. The species is similar to Micranthemum tweediei “Monte Carlo” but has more rounded leaves and grows more vertically.
Light Requirements
Pearlweed accepts a wide range — 40-150 µmol PAR at substrate. Under 40 µmol it stretches into vertical strands chasing light; above 100 µmol it stays compact and bushy. For carpet behaviour, target 80-120 µmol. The LED fixture range includes mid-power options that hit this PAR window on tanks up to 60 cm tall.
CO2 and Carbon
Without CO2 injection, pearlweed grows but slowly and stretches vertically. With 30 ppm CO2, it carpets aggressively — plant cuttings 3 cm apart fill in within 6-8 weeks. Liquid carbon supplements (Excel, Tropica Easy Carbo) at label dose work as middle-ground for low-tech tanks. The plant tolerates the brief Excel exposure that melts Vallisneria, making it a flexible choice for mixed tanks.
Substrate and Root Feeding
Pearlweed is a column feeder primarily but benefits from nutrient-rich substrate. Aquasoil from the substrate range works perfectly; inert substrates like sand or gravel demand stronger column dosing to compensate. Roots are fine and shallow — they anchor in 2-3 cm of substrate without issue. Root tabs help in inert setups but are unnecessary in fresh aquasoil.
Water Parameters
Temperature 22-28°C, pH 6.0-7.5, GH 2-12, KH 1-8 — the species accepts almost any sane planted-tank parameter range. Singapore PUB tap at GH 2-4 and pH 7.0-7.2 is fine; remineralise lightly with GH booster to 5-6 if running heavy stem-plant scapes alongside. The plant melts only at extremes (pH below 5.5, GH above 18) that few keepers encounter.
Planting Technique
Cut stems into 5 cm lengths, strip the bottom 2 cm of leaves, and plant individual stems 2-3 cm apart in a grid. Use long-handled aquascaping tongs from the tools section to push stems firmly into substrate without crushing the apical tip. For midground bushes, plant in clusters of 6-10 stems; for carpets, evenly spaced grids work better.
Trim and Propagation
Trim every 3-4 weeks once the plant fills in. Cut horizontally with sharp scissors at 5-7 cm height; the stems below branch laterally and density increases with each trim. The trimmed tops can be replanted directly to expand the area or fill gaps. Floating cuttings root within a week if left alone, which means small fragments can colonise unintended corners — pull these promptly.
Tank Mate Compatibility
Pearlweed handles most planted-tank fish without issue. Avoid silver dollars, large goldfish, and most cichlids that uproot stem plants. Shrimp adore the dense fronds for grazing biofilm. Otocinclus eat pearlweed biofilm without damaging stems. The plant’s small leaves and dense growth make it ideal cover for fry.
Common Issues
Yellow lower leaves: nitrogen famine, bump NO3 to 10-15 ppm. Leggy vertical growth with sparse leaves: insufficient light, raise PAR or shorten the stems to push branching. Brown holes: potassium deficit, dose 5-10 ppm K weekly. White stem rot at substrate level: anaerobic pocket forming, vacuum substrate and increase circulation. Most issues resolve within two weeks of correction.
Singapore Sourcing and Pricing
Pearlweed sells at SGD 5-12 per pot at most local shops including Gensou, C328 in Clementi, and the Serangoon North aquarium row. Tissue-culture cups (SGD 10-15) from Tropica or Dennerle reduce snail and pest risk versus loose stems. Buying from vetted plant suppliers means tracked source and predictable health on arrival. A SGD 10 portion provides 30-40 plantable stems — enough for a 60 cm tank’s mid-ground.
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