Rotala wallichii: the pink needle stem

Where it comes from

Rotala wallichii grows in soft, acidic waters across South and Southeast Asia. Among the many Rotala species it is prized — and feared — for its delicate, feathery form and intense colour.

What to expect

Slender stems carry dense whorls of hair-fine needle leaves. Under weak light it is a modest green; under strong light with CO2 the tops flush pink, orange and red, forming a soft, colourful bush that few other plants can match. It is a very different texture from the round-leaved Rotala rotundifolia.

How to keep it

This is a high-tech plant. It wants soft, acidic water, strong light, stable CO2 and steady dosing — including iron to drive the red. In a low-tech tank it grows thin, green and reluctant, and often melts. If your tank is not CO2-injected, choose the far tougher Rotala rotundifolia instead.

Parameter	Value
Lighting	High — colour and form both need it
CO2	Required for reliable growth
Temperature	22–28 °C
pH	5.5–7.0 — prefers soft water
Hardness	Soft
Fertiliser	Regular dosing; iron for colour
Substrate	Nutrient-rich aquasoil
Growth rate	Fast (given light + CO2)
Placement	Background, Midground
Difficulty	Advanced

Where it works and how to spread it

Plant many stems close together as a group — wallichii looks best massed, where the fine texture reads as a soft cloud. Top and replant the cuttings to propagate and to thicken the stand. Frequent trimming keeps it dense and colourful.

What goes wrong

Melting and thin, colourless growth are the usual heartbreaks, and both come down to unstable CO2, insufficient light, or hard water. It is sensitive to change, so keep conditions steady. Reward for the effort is one of the most beautiful plants in the hobby.

More plants in this series

• Rotala rotundifolia — the tough, easy Rotala
• Alternanthera reineckii — the broad-leaved red plant