Dwarf Hemianthus

The carpet everyone wants — a tight, even mat of tiny bright green leaves at 1 to 3 cm tall — is achievable but fragile. Hemianthus callitrichoides, known as HC Cuba or Dwarf Baby Tears, is the most demanding foreground plant in common cultivation. It does not settle for approximation: the gap between growing it and growing it well is narrow.

Light intensity is the gate. The plant needs strong light across the entire carpet area; any shadowed patch stretches upward and looks thin. CO₂ injection is equally critical — without it the stems elongate, the leaves shrink, and the ground cover effect unravels. Stable CO₂ in the 20 to 40 mg/l range keeps it compact.

It comes from seasonal pools on the Caribbean island of Cuba. In the aquarium it does best at 24 to 26 °C and pH 5 to 7 in soft, nutrient-rich water. Hard alkaline water stalls growth. Iron and nitrate must be available but not excessive — high nitrate coaxes the stems upward rather than outward.

Planting in small clumps a couple of centimetres apart rather than one dense mat gives the runners room to spread into the gaps. Trimming with scissors at about 1 cm every week or two forces lateral branching and keeps the carpet dense. A patch that lifts from the substrate can be pinned down with a small piece of rock or plant weight until it roots.