Micranthemum micranthemoides
Often mislabelled HC Cuba. Tiny round leaves on slender stems, under high light + CO₂ stays low and creates a fuzzy carpet; under low light grows tall and stem-like. Pearls heavily under CO₂ (hence the name). A more forgiving foreground option than true HC.
Pearlweed (Micranthemum micranthemoides) is a stem (creeping or vertical) aquatic plant for the foreground to midground of a planted tank. It reaches 5–25 (varies hugely with light) cm under good conditions and grows at a fast rate. Light: medium to high. CO₂: optional. Target 20–28 °C, pH 5.5–7.5, and 2–15 dGH. Substrate: Any, water column feeder. Propagate via cuttings.
Care at a glance
Often mislabelled HC Cuba. Tiny round leaves on slender stems, under high light + CO₂ stays low and creates a fuzzy carpet; under low light grows tall and stem-like. Pearls heavily under CO₂ (hence the name). A more forgiving foreground option than true HC.
By Mike ElmiraUpdated 2 min read
Part of our complete guide to the planted aquarium.
The parameters that decide whether pearlweed fits in your tank.
Linderniaceae
Stem (creeping or vertical)
Foreground to Midground
Any, water column feeder
Cuttings
Damp wooded streams and bogs of Eurasia
Eastern and southern USA, Cuba
Tank-mate safety and the species this one is documented to thrive (or fail) alongside.
Hard-won lessons from the tank.
The forgiving alternative to HC Cuba. Skip CO₂ for a taller, looser carpet over 6–8 weeks; add CO₂ for a tight pearling foreground in 3–4 weeks. The pearling under high light + CO₂ is genuinely spectacular — single fronds become tiny oxygen-bubble factories. One of the most photographed plants in competition aquascapes.
What can go wrong and how to spot it.
Failure modes, in order of how dramatic the fix is.
Stretchy upward growth (instead of carpeting): insufficient light. Pale: iron + nitrogen. Stunted: CO₂ instability or low light.
Less prone to algae than HC Cuba due to faster growth. BBA on older lower portions if flow is poor.
The practical routine, read top to bottom.
Light water-column feeder. Standard EI dosing or commercial all-in-one suffices. CO₂ optional — speeds growth significantly and triggers pearling.
Top every 2–3 weeks to encourage horizontal spreading (for foreground use) or just remove damaged stems (for midground use). Cuttings root within days.
Where it comes from, how it behaves, and the variants you'll see at retail.
Where it lived before it came home.
Slow streams, swamps, and pond margins across the southeastern United States and Cuba. Grows emersed in damp mud or fully submerged in shallow water.
Vigorous emersed grower with stiffer leaves. Tissue culture typically delivers emersed form; transitions to submerged within 1–2 weeks with softer slightly larger leaves.
Tiny inconspicuous emersed flowers; never flowers submerged.
The named cultivars and the lookalikes worth flagging.
H. glomeratus is the most common pearlweed in trade. Often mislabelled and sold as 'HC Cuba' or 'pearlweed Cuba' — true HC Cuba is the much smaller Hemianthus callitrichoides. Check leaf size: pearlweed leaves are 4–6 mm; HC Cuba leaves are 2–3 mm.
Often sold as 'HC Cuba' or 'Cuba Pearlweed' in confusion. True HC Cuba is much smaller and demands CO₂; pearlweed is forgiving. Verify by leaf size at purchase.
Direct answers to the questions search engines and AI assistants surface most often about this species.
CO₂ requirement: optional. Light requirement: medium to high. Under low-tech conditions the plant grows at a fast rate.
Pearlweed (Micranthemum micranthemoides) needs medium to high light. Run a photoperiod of 6–8 hours; longer photoperiods invite algae unless CO₂ and dosing are dialled in.
Position: foreground to midground. Substrate: Any, water column feeder It typically reaches 5–25 (varies hugely with light) cm.
Propagation method: Cuttings. Pearlweed is a stem (creeping or vertical) plant.
Target 20–28 °C, pH 5.5–7.5, and 2–15 dGH. Flow tolerance: low to medium.
Difficulty: 2/5. Forgiving, beginner-friendly once the tank is cycled.
A planted tank is a system. Pair this plant with one entry from each other pillar to plan the whole scape.
