Rotala macrandra 'Japan' (Japanese loosestrife)

13 October 2026

Rotala macrandra 'Japan' is a red-leaved aquarium stem plant sold under the common name Japanese loosestrife. It is generally regarded as a demanding form of Rotala macrandra and needs strong light, reliable carbon dioxide and consistent nutrition to maintain compact growth and good coloration. The supplied images support this identification, but cultivar names in aquarium commerce are not always standardized, so the exact form cannot be confirmed from images alone.

Rotala macrandra 'Japan' (Japanese loosestrife)

Identification

This plant forms upright stems with opposite, relatively broad leaves. Under suitable submerged conditions, the foliage can range from copper and orange to pinkish red or deep red. Rotala macrandra 'Japan' is best treated as a cultivated aquarium form rather than a separately verified wild species. Similar red Rotala forms can look alike, so the cultivar identification remains provisional without provenance or additional diagnostic information.

Placement and planting

Use it as a background or tall midground group in an open area with good water movement. Plant individual stems separately, leaving a small gap between them so light can reach the lower foliage. Avoid burying the leaves or packing the stems tightly, as poor circulation and shading can encourage lower-leaf loss.

Light and carbon dioxide

High light is usually needed for dense growth and stronger red coloration. Pressurized carbon dioxide is strongly recommended; unstable carbon dioxide commonly produces weak, sparse growth and algae problems. Keep the photoperiod consistent and avoid increasing light before carbon dioxide delivery and circulation are stable.

Water and nutrition

Maintain stable, clean aquarium conditions with regular water changes. Provide a complete supply of nitrogen, phosphorus, potassium and trace elements, while avoiding abrupt changes in fertilization. A nutrient-rich substrate can support rooting, although this stem plant also takes substantial nutrition from the water column. Monitor new growth and adjust dosing gradually rather than making large corrections.

Propagation and pruning

Propagation is normally by cuttings. Trim healthy upper sections and replant them after removing the lower leaves from the buried portion. Repeated trimming encourages branching and creates a denser group. Remove shaded or deteriorating lower stems, and replant vigorous tops when the original bases become bare.

Plant info

Colors: Red, Orange, Pink
Difficulty: Advanced
Origin: Cultivar
Usage: Background
Type: Aquatic stem plant
Growth rate: Medium
Height: 20-50 cm
Light demand: High
CO2: High

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