Rotala wallichii

Rotala wallichii originates from the streams, rice paddies, and marshy areas of Southeast Asia, including Thailand, Myanmar, and surrounding countries. It is one of the finest-leaved stem plants available in the aquarium trade, with needle-thin, pinkish-red leaves arranged densely in whorls around delicate stems. Under strong light and CO2 enrichment the leaves achieve an intense crimson or magenta colouration that is truly spectacular, making it one of the most photographed and desired plants in competitive aquascaping. However, this beauty comes with stringent requirements: R. wallichii is highly sensitive to water hardness, alkalinity, and any form of nutrient deficiency. In hard or alkaline water the delicate leaves deteriorate rapidly, and the plant rarely performs well outside carefully managed soft-water, high-tech setups. It also dislikes strong currents that may damage the fragile leaf whorls. When conditions are met, it grows at a moderate pace and maintains stunning colour. In competition aquascaping it is often used as a vivid colour accent in the background, arranged behind larger, more robust green plants to maximise contrast.

Placement Best used as a background accent in high-tech aquariums with soft water. Plant in tight groups of 5–8 stems. Avoid strong direct current from filter outlets to protect fragile leaves.

Lighting Very high lighting (80–120 PAR) is required to achieve deep red colouration. Under moderate light the plant turns pale and may eventually decline. Run photoperiod of 8–9 hours maximum to avoid algae.

CO2 & Fertilisation CO2 injection at 25–35 ppm is mandatory. Comprehensive fertilisation with Estimative Index or similar method is required, with elevated iron (0.3–0.5 ppm) and potassium. Soft water below 8° GH is important.

Propagation Top cuttings of 5–8 cm replanted carefully in substrate. Roots form slowly over 10–14 days. Handle stems gently to avoid damaging the fragile whorls. Side shoots develop after trimming but are sparse compared to other Rotala species.

Trimming Trim carefully every 3 weeks, cutting just above a whorl. Replant the colourful top portions. Discard bare lower stems. Stability during and after trimming is critical — avoid changing water parameters simultaneously.