Hemianthus callitrichoides 'Cuba' (HC Cuba) care

Light

Aim for at least 4-6 hours of direct sun on the leaves. Submerged carpeting plant needing high aquarium light (roughly 50+ PAR at substrate) to grow flat and dense. Under weak light it grows tall and leggy, reaches for the surface, and fails to carpet. If your only bright window faces south, that's perfect for hemianthus callitrichoides 'cuba' — same window any aroid would fry on.

Watering

Watering hemianthus callitrichoides 'cuba': permanently submerged; 30-50% water change weekly. The number that matters isn't the day of the week — it's how dry the top 2-3 cm of the pot feels. A finger in the soil tells you more than a watering app. After every watering, tip the saucer. Keep underwater in soft to moderately hard, slightly acidic water, pH 5.5-7.0. Frequent water changes during establishment limit algae on the slow-knitting carpet; it dislikes high temperatures, which thin the growth.

Soil and pot

Hemianthus callitrichoides 'Cuba' grows best in nutrient-rich aquasoil. Plant tiny portions into fine, nutrient-rich aquasoil; the substrate supplies much of its feeding while the roots are shallow. A rich active soil is close to essential for a healthy carpet. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Hemianthus callitrichoides 'Cuba' sits happiest at around 100% (submerged) humidity and 21-26°C (70-79°F). An aquatic carpeting plant grown fully underwater, so ambient humidity is irrelevant. It is often started emersed in near-saturated, lidded trays before flooding the tank. If you keep the room above 21 year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed hemianthus callitrichoides 'cuba' sparingly. Requires consistent nutrients: pressurised CO2 plus a full water-column fertiliser regime (macros and traces) on top of rich aquasoil. Lean dosing or missing CO2 stalls the carpet and invites algae; iron supports the bright-green colour. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on hemianthus callitrichoides 'cuba' in the Growli community. Each is annotated with the most common cause so you know where to start.

• Carpet lifting / floating up — Mats detach from the substrate as gas builds beneath or roots stay shallow. Plant in small portions, press in firmly, keep CO2 and flow steady, and trim to encourage rooting.
• Algae during establishment — Slow early growth lets spot and hair algae colonise the bare soil. Run lean nutrients early, add cleanup crew (shrimp, otocinclus), and ramp light gradually.
• Leggy, vertical growth — Insufficient light makes it stretch upward instead of carpeting. Increase intensity and ensure strong CO2 to keep growth compact and horizontal.
• Melt without CO2 — Without pressurised CO2 it commonly thins and dies back. Treat CO2 as a requirement, not an option, for a lasting carpet.

Propagation

Vegetative: lift a patch of established carpet, separate it into small portions, and replant each into substrate to spread. Each section roots and creeps outward to form new carpet. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Hemianthus callitrichoides 'Cuba' is mildly toxic to pets. Hemianthus callitrichoides is not individually listed in the ASPCA Toxic and Non-Toxic Plants database, so its pet status is not formally established; treat as uncertain and verify with a vet before assuming it is safe to ingest. No specific toxic principle is documented, but absence of an ASPCA listing is not a safety guarantee. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Hemianthus callitrichoides 'Cuba' deep-dive guides

Every aspect of hemianthus callitrichoides 'cuba' care, each with its own calibrated guide:

• Hemianthus callitrichoides 'Cuba' watering schedule
• Hemianthus callitrichoides 'Cuba' light requirements
• Best soil mix for hemianthus callitrichoides 'cuba'
• Hemianthus callitrichoides 'Cuba' fertilizing guide
• When to repot hemianthus callitrichoides 'cuba'
• How to propagate hemianthus callitrichoides 'cuba'
• Hemianthus callitrichoides 'Cuba' growth rate & size
• Hemianthus callitrichoides 'Cuba' cold hardiness
• Hemianthus callitrichoides 'Cuba' temperature & humidity
• Is hemianthus callitrichoides 'cuba' toxic to cats & dogs?
• Is hemianthus callitrichoides 'cuba' toxic to cats?
• Is hemianthus callitrichoides 'cuba' toxic to dogs?

Featured in these plant shortlists

Hemianthus callitrichoides 'Cuba' qualifies for 2 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best small & tabletop houseplants — Compact houseplants that stay under about 40 cm — desk, shelf and windowsill plants that never outgrow a small space.
• Best houseplants for full sun — Houseplants that want direct sun — the species for a hot south or west-facing windowsill where shade-lovers scorch.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Hemianthus callitrichoides 'Cuba' is also commonly called HC Cuba or dwarf baby tears.

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