Rotala macrandra (giant red Rotala) care

Light

Bright but filtered. Rotala macrandra burns within days in unfiltered south-facing summer sun, and stops growing within months in deep shade. Submerged plant requiring high-intensity aquarium light (roughly 60-100+ PAR) for its signature red colour and compact form. Under weaker light it grows greenish, leggy and pale. If you only have a south window, set the plant back 1.5 m or hang a sheer curtain — both knock the intensity down into the right range.

Watering

Watering rotala macrandra: submerged permanently; 30-50% aquarium water changes weekly. The number that matters isn't the day of the week — it's how dry the top 2-3 cm of the pot feels. A finger in the soil tells you more than a watering app. After every watering, tip the saucer. Grows underwater in freshwater. Prefers soft to moderately hard water (2-10 dGH), pH 6.0-7.0. Stable pressurised CO2 (25-35 ppm) is effectively essential; it does not tolerate CO2 swings.

Soil and pot

Rotala macrandra grows best in nutrient-rich aquasoil substrate. Best rooted in active aquasoil with root tabs. A fertile substrate plus lean water-column dosing supports the strong, well-coloured growth this species demands. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Rotala macrandra sits happiest at around 100% (submerged aquatic) humidity and 24-28°C (75-82°F). Cultivated fully underwater, so ambient humidity is irrelevant. Emersed growth is possible in a humid setup but the leaves and colour differ markedly from the submerged red form. If you keep the room above 24 year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed rotala macrandra sparingly. Dose a complete macro and micro fertiliser regimen with emphasis on iron and trace elements for red intensity; keep nitrate lean. Consistency matters more than dose size, as macrandra stunts under fluctuating nutrients or CO2. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on rotala macrandra in the Growli community. Each is annotated with the most common cause so you know where to start.

• Stunted, deformed new tips — The classic macrandra problem, caused by CO2 swings or micronutrient shortfall. Stabilise CO2 across the full photoperiod and ensure adequate magnesium, calcium and trace elements.
• Poor red colour — Needs high light, lean nitrate and good iron. Raise PAR and iron dosing; excess nitrate pushes it toward green.
• Lower-leaf melt and rot — Often from low flow, shading or transition from emersed stock. Improve circulation, thin the canopy, and replant healthy tops.
• Algae on broad leaves — Its large leaf surface and moderate pace invite algae if light outpaces CO2. Balance light to CO2 and keep nutrients steady.

Propagation

Cut the top 5-8 cm of a healthy stem and replant; the parent stem branches at the cut. Use vigorous tops for propagation, as stunted material often fails to recover. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Rotala macrandra is mildly toxic to pets. Rotala is not individually listed by the ASPCA on either the toxic or non-toxic plant lists, so its pet status is unconfirmed. Treat with caution and verify with a vet; as a submerged aquarium plant, ingestion by cats or dogs is unlikely in practice. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Rotala macrandra deep-dive guides

Every aspect of rotala macrandra care, each with its own calibrated guide:

• Rotala macrandra watering schedule
• Rotala macrandra light requirements
• Best soil mix for rotala macrandra
• Rotala macrandra fertilizing guide
• When to repot rotala macrandra
• How to propagate rotala macrandra
• Rotala macrandra growth rate & size
• Rotala macrandra cold hardiness
• Rotala macrandra temperature & humidity
• Is rotala macrandra toxic to cats & dogs?
• Is rotala macrandra toxic to cats?
• Is rotala macrandra toxic to dogs?

Featured in these plant shortlists

Rotala macrandra qualifies for 2 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best plants for a north-facing window — Houseplants for a north-facing window: bright, even, indirect light and no scorching direct sun. Each pick verified against its documented light needs.
• Best small & tabletop houseplants — Compact houseplants that stay under about 40 cm — desk, shelf and windowsill plants that never outgrow a small space.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

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