Alternanthera cardinalis: easy red plant for a natural aquarium
A red plant that adds contrast
Alternanthera cardinalis is one of the best plants for adding red and depth to a layout. The tops of the leaves remain slightly greener, while the undersides turn pink-red, creating highly visible shades and gradients in a bush.
Easy to grow successfully, it is suitable for low-tech tanks and can be propagated indefinitely.
Why choose Alternanthera cardinalis?
- More intense red color under strong light; the contrast is immediate.
- Low-tech compatible: grows without CO2, and neither fertilizer nor technical soil is necessary.
- Extremely easy to propagate (cut tops and replant them, stem cuttings, horizontal layering).
- Background and midground: creates beautiful, dense, structurally defining bushes.
- A robust plant for beginners (simple substrate, very flexible parameters).
- Very valuable in aquascaping for creating focal points.
Growing tips (simple and effective)
- Light: medium to high (the stronger it is, the redder and more compact the plant will be).
- Substrate: plain sand is sufficient. With fish, shrimp, or other animals present, no fertilizer is needed. The iron in their waste is also sufficient.
- CO2: completely unnecessary in a low-tech setup. In fact, fish or shrimp respiration 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: does not survive the winter outdoors. Aquarium plant, even in an unheated aquarium.
Use in aquascaping
- Strong contrast with green plant clusters. Subtle red, slightly metallic.
- Background placement to add depth, or in the midground to stand out against a green background.
- Regular pruning for a dense bush and a stockier shape. Remember to replant the cut portions!
Advantages in a low-tech aquarium
- Hardy, versatile, and adaptable (no specialized substrate required).
- Red color without CO2 or added iron if the lighting is adequate.
- Easy propagation: economical and quick to maintain.
FAQ - Alternanthera cardinalis
Is CO2 needed to achieve a bright 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 gets enough light. It is not particular about the substrate.
How should I prune it for a dense bush?
Cut and replant the tops. The base will produce new shoots. Repeat to make the clump denser.
Why is my Alternanthera turning green?
Often insufficient lighting or an iron deficiency (for example, when there are no fish): increase the light and introduce animals (fish, shrimp, microfauna). In rare cases, add an iron supplement.
Do goldfish eat it?
Some herbivorous fish may indeed nibble on its fine leaves: exercise caution in affected tanks.
Additional information
- Scientific name: Alternanthera cardinalis
- Plant type: red stem plant
- Light: medium to high; its red color is enhanced by light intensity.
- Temperature: 18 to 28°C. It does not tolerate cold: for aquarium use only, even in an unheated tank.
- Size: 30 to 50 cm in an aquarium (may emerge in an open-top tank).
- Packaging: 3 stems (approximate weight: 20 g).
- Guarantee: no 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 preserve our ecosystems.
