The Dwarf Baby Tears Care Guide: Carpeting with HC Cuba

Hemianthus callitrichoides 'Cuba' — HC Cuba, Dwarf Baby Tears — produces the smallest and finest carpet available in the hobby. It is also one of the few plants where the difficulty rating is not negotiable. High light and pressurised CO2 are requirements, not recommendations.

If you do not have both, read the last section of this guide before ordering.

Planting: small clumps, spaced out

Separate your portion into clumps of five to ten stems each. Plant each clump about half an inch to an inch apart across the substrate.

Two mistakes are common:

• Planting one large mass. It shades its own centre, rots in the middle and lifts.
• Planting too deep. Only the base needs to be in the substrate. Buried stems rot.

Use fine substrate. HC has short delicate roots that cannot grip coarse gravel, and clumps float free before they anchor.

Plant into damp substrate rather than a filled tank where possible — fill slowly afterwards onto a plate or bag to avoid washing the clumps out.

The dry start method is the reliable route

The most consistent way to establish an HC carpet is to not fill the tank at first.

1. Plant into damp substrate, with a shallow water level just below the surface.
2. Cover the tank with cling film or a lid to hold humidity near 100%.
3. Run lights on a normal photoperiod.
4. Mist as needed to keep the substrate damp, and air the tank briefly every few days to prevent mould.
5. After four to eight weeks, once the carpet has closed, flood the tank slowly.

Grown emersed this way, HC establishes a dense rooted carpet with no CO2 and no algae competition. You still need CO2 once flooded — the dry start buys you a healthy carpet to start from, not an exemption.

Expect a transition period after flooding as the emersed growth converts to submersed form.

Why carpets detach and float

A mature HC carpet that lifts off the substrate in sheets is not diseased. Two things cause it.

Oxygen underneath. A healthy carpet pearls, and oxygen collects between the mat and the substrate until the whole sheet floats free.

The carpet grew too thick. As HC layers over itself, the bottom layer is cut off from light, dies, and stops holding on.

The fix for both is the same: trim regularly. Cut the carpet back to roughly half its thickness every few weeks with sharp scissors and remove the clippings. A trimmed carpet stays anchored; an untrimmed one eventually lifts.

Melting and CO2 stability

HC responds badly to changing CO2. A steady, adequate level matters more than a high one — an interruption, a clogged diffuser or a solenoid failure will show up as melt within days.

It is also intolerant of high temperature. Above the upper seventies it thins and struggles, so this is not a good carpet for a warm discus tank.

HC Cuba is not Monte Carlo

These are the two plants people compare, and the difference matters a great deal.

• HC Cuba — tiny round leaves a few millimetres across, the finest carpet available. High light, CO2 required, advanced.
• Monte Carlo (Micranthemum tweediei) — noticeably larger leaves, coarser carpet, but far more forgiving. Grows in medium light and will carpet without CO2, though more slowly.

If you do not run pressurised CO2, choose Monte Carlo. It gives you a carpet you will actually keep. HC in a low-tech tank does not fail dramatically — it thins, stretches, collects algae and disappears over a couple of months.

Quick reference

• Light — High
• CO2 — Required
• Water — 68–78°F, pH 6.0–7.0
• Feeding — Water column, with fine nutrient substrate
• Height — 1–2 in
• Propagation — Runners
• Difficulty — Advanced

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