Overview & Origin
Hemianthus callitrichoides (commonly called HC Cuba, HC, or Dwarf Baby Tears) was discovered in Cuba by Holger Windelov of Tropica and introduced to the aquarium hobby in 2003. It quickly became the most sought-after carpet plant due to its incredibly tiny leaves (just 2–3mm across) that form the densest, most detailed carpet possible in an aquascape.
In competition aquascaping, HC Cuba is the most commonly used foreground carpet for Iwagumi and nature-style layouts where a perfectly manicured green carpet is essential. Its diminutive size creates a powerful sense of scale, making rocks and driftwood appear much larger by comparison.
Requirements — What HC Cuba Needs
HC Cuba is the most demanding common carpet plant. Here's what it absolutely requires:
- High light: Minimum 50 PAR at substrate level, ideally 70–100 PAR. Insufficient light is the #1 reason HC Cuba fails.
- CO2 injection: Essentially mandatory. Target 30+ ppm. Without CO2, HC Cuba will grow extremely slowly if at all, and usually dies within weeks.
- Fine substrate: Very fine-grained aquasoil (ADA Amazonia, Tropica Aquarium Soil). The tiny roots cannot anchor in coarse substrate.
- Consistent fertilization: All-in-one liquid fertilizer 3x per week plus root tabs. HC Cuba is a heavy feeder for its size.
- Clean water: Regular water changes (30–50% weekly) to prevent organic buildup that promotes algae on the delicate leaves.
How to Plant HC Cuba
Planting HC Cuba requires patience and precision:
- Separate tissue culture portions into very small clumps (5–8 stems each).
- Using fine-tipped planting tweezers, push each clump deep into the substrate at a 45-degree angle, leaving only leaf tips visible.
- Space clumps 1–1.5 inches apart in a grid pattern.
- Plant the entire foreground area at once — partial planting leaves bare areas that algae will colonize before HC can spread to cover them.
Dry start method: HC Cuba responds exceptionally well to the dry start technique. Plant in moist substrate with no standing water, cover with plastic wrap, and mist daily with a spray bottle. After 6–8 weeks of dense emersed growth, slowly flood the tank. This gives HC Cuba a massive head start and greatly reduces the risk of uprooting and algae during the critical establishment phase.
Water Parameters
- Temperature: 68–77°F (20–25°C) — prefers cooler temperatures
- pH: 5.5–7.5
- KH: 0–4 dKH
- GH: 2–8 dGH
- CO2: 30+ ppm (mandatory)
HC Cuba prefers soft, slightly acidic water. It can struggle in hard, alkaline water — if your tap water is very hard, consider mixing with RO water.
Maintenance
- Trimming: Regular mowing is essential. When the carpet exceeds 1 inch thick, the bottom layers die and the carpet detaches. Trim every 2–3 weeks with flat scissors.
- Pearling: When conditions are ideal, HC Cuba produces visible oxygen bubbles (pearling) — a beautiful effect and a sign that the plant is photosynthesizing heavily.
- Water changes: 30–50% weekly to maintain water clarity and prevent organic waste buildup.
Common Problems & Solutions
- Carpet floating/uprooting: The most common issue. Caused by gas accumulation under the carpet, bottom layers dying, or insufficient root anchoring. Replant floating sections and trim the carpet thinner.
- Yellowing or melting: Insufficient CO2, light, or nutrients. Check all three and increase as needed.
- Algae takeover: HC Cuba's slow initial growth makes it vulnerable to algae. Ensure CO2 is at 30+ ppm, limit photoperiod to 6–7 hours during establishment, and add algae-eating shrimp.
- Not spreading: Most likely a CO2 or light deficiency. HC Cuba won't carpet without both at adequate levels.
Frequently Asked Questions
Can HC Cuba grow without CO2?
In submersed form, practically no. Some hobbyists report marginal survival without CO2, but it will not form a carpet. The dry start method (emersed growth) works without CO2 but you'll need to add CO2 once the tank is flooded.
HC Cuba vs Monte Carlo — which should I choose?
If you have a high-tech setup with CO2 and strong lights, HC Cuba creates a more delicate, detailed carpet. If you want an easier carpet that works in low-tech setups, choose Monte Carlo. For beginners, Monte Carlo is always the better choice.
Why does my HC Cuba keep floating?
Gas buildup under the carpet, dead bottom layers, or the carpet being too thick. Trim regularly, plant deeper, and ensure the substrate is fine enough for root anchoring.