Author: Bryce Millar, MD
Common Names: Giant red rotala
Native Distribution: India
Aquarium Placement: Focal point
Requirements: Intense lighting, CO2 recommended
Rotala macrandra has a well-deserved reputation as a favorite in the aquarium hobby. When it comes to intense coloration, it has few equals and is sometimes known as “king of the reds.” Its appearance can be quite stunning when in top condition.
Unlike the majority of Rotala, it is rather demanding in its requirements. It is best suited to aquariums with high-intensity lighting and will not tolerate shading. Individual stems should be planted far enough apart to ensure that lower regions get adequate light. If not, lower portions of the primary stem can waste away, leaving the top to break free. Carbon dioxide supplementation is not strictly required, but if used it will greatly help to create the overall environment necessary to keep this species.
Despite its demanding nature, once established Rotala macrandra can grow rather quickly. In ideal conditions growth can be up to 3 or 4 inches per week. Proper nutrient levels are important to keep it in top form. An intense deep-red coloration is often achieved by keeping phosphate levels relatively high (1.5 to 2.0 ppm) while keeping nitrates on the low side (10 ppm or less). Higher nitrate levels will result in light orange growth. Stunting of the growing tips often indicates a lack of micronutrients. Insufficient nitrate levels can also mimic insufficient light, causing lower portions of the plant to waste away.
In addition to the standard specimen, interesting varieties and cultivars are also available in the hobby. These include Rotala macrandra “green,” Rotala macrandra “narrow leaf,” and Rotala macrandra “variegated.” A conclusive taxonomic description of these varieties is not yet available. Most of these are somewhat less demanding but no less useful in creating an effective aquascape.
R. macrandra is best used sparingly, as its strong coloration can overwhelm an otherwise well-balanced scene. A few well-positioned stems provide a strong point of visual interest. Situating this species against a backdrop of light-green plants will even further accentuate its beauty. Dutch-style aquariums often feature this plant in cascading “streets.” A single stem can also be used to create an accent in small- or medium-sized aquaria.
Notes: If Rotala macrandra finds conditions to its liking, it will branch extensively, especially as it grows closer to the aquarium light source. Simple trimming of the upper portions as one would do for other stem plant species can be done, but it is often better to allow it to grow to the top of the aquarium, uproot it, and replant only the younger upper portions.