Alternanthera cardinalis: red, easy-care plant for a natural aquarium
A red plant that adds contrast
Alternanthera cardinalis is one of the best plants for adding red tones and depth to an aquascape. The upper side of the leaves remains slightly greener, while the underside turns pink-red, creating highly visible shades and gradients in a bushy group.
Easy to grow successfully, it is suitable for low-tech tanks and can be propagated endlessly from cuttings.
Why choose Alternanthera cardinalis?
- More intense red color under strong lighting; the contrast is immediate.
- Low-tech compatible: grows without CO2, and no fertilizer or specialized substrate is required.
- Extremely easy propagation (cut tops and replant them, stem sections, horizontal layering).
- Background and midground: creates beautiful, dense, structural bushes.
- Hardy plant for beginners (simple substrate, very flexible parameters).
- Highly valuable in aquascaping for creating focal points.
Growing advice (simple and effective)
- Lighting: medium to strong (the stronger it is, the redder and more compact the plant will be).
- Substrate: simple sand is sufficient. With fish, shrimp, or other animals present, no fertilizer is needed. The iron contained in their waste is also sufficient.
- CO2: completely unnecessary in a low-tech setup. Fish or shrimp respiration already provides enough.
- Parameters: soft to moderately hard water. A truly tolerant plant as long as the water is not extreme.
- Pruning: cut above a node and replant the top; the base will produce new shoots.
- Temperature: it does not survive winter outdoors. It is an aquarium plant, even in an unheated aquarium.
Use in aquascaping
- Powerful contrast with green plant groups. Nuanced, slightly metallic red.
- Place it in the background to add depth, or in the midground to stand out against a green backdrop.
- Prune regularly for a dense bush and a more compact shape. Remember to replant the cut sections!
Advantages in a low-tech aquarium
- Hardy, versatile, and adaptable (no specialized substrate required).
- Red color without CO2 or added iron when the lighting is adequate.
- Easy propagation: quick and economical maintenance.
FAQ - Alternanthera cardinalis
Is CO2 required to achieve a vivid red color?
No, but strong lighting enhances the color even further.
Can it live in a low-tech setup?
Yes. It grows well without CO2, provided it receives enough light. It is not demanding about the substrate.
How should I prune it to create a dense bush?
Cut and replant the tops. The base will produce new shoots. Repeat to thicken the group.
Why is my Alternanthera turning green?
Often because of insufficient lighting or a lack of iron (for example, when there are no fish): increase the lighting and add animals (fish, shrimp, or microorganisms). In rare cases, add an iron supplement.
Do goldfish eat it?
Some herbivorous fish may indeed nibble its thin leaves: use caution in affected tanks.
Additional information
- Scientific name: Alternanthera cardinalis
- Plant type: red stem plant
- Lighting: medium to strong; its red color is enhanced by light intensity.
- Temperature: 18 to 28°C. It does not tolerate cold; reserve it for the aquarium, even an unheated one.
- Size: 30 to 50 cm in an aquarium (may grow above the water in an open tank).
- Packaging: 3 stems (indicative weight: 20 g).
- Guarantee: without rock wool or any artificial substrate of any kind.
- Recommendation: as a precaution, please never release this plant into the wild. It is not native to our regions and should obviously not become naturalized, but we must protect our ecosystems.
