Alternanthera cardinalis: an easy red plant for natural aquariums
A red plant that adds contrast
Alternanthera cardinalis is one of the best plants for adding red and depth to a layout. The upper side of the leaves remains a little greener, while the underside turns pink-red, creating highly visible shades and gradients in a bush.
Easy to grow successfully, it suits low-tech tanks and can be propagated endlessly.
Why choose Alternanthera cardinalis?
- More intense red color under strong light; the contrast is immediate.
- Low-tech compatible: grows without CO2, and no fertilizer or specialized substrate is needed.
- Extremely easy to propagate (cut tops and replant, stem sections, horizontal layering).
- Background and midground: creates beautiful, dense, structured bushes.
- Hardy plant for beginners (simple substrate, very flexible parameters).
- Highly valued 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).
- Substrate: simple sand is enough. With fish, shrimp, or other animals, no fertilizer is needed. The iron in their waste is also sufficient.
- CO2: completely unnecessary in low-tech tanks. In fact, fish or shrimp respiration provides enough.
- Parameters: soft to moderately hard water. A very tolerant plant as long as the water conditions are not extreme.
- Pruning: cut above a node and replant the top; the base will produce new shoots.
- Temperature: does not survive winter outdoors. Aquarium plant, even in an unheated tank.
Use in aquascaping
- Strong contrasts with green plants. Nuanced red, slightly metallic.
- Background placement to add depth, or in the middle to stand out against a green background.
- Prune regularly for a dense bush and a more compact shape. Remember to replant the cuttings!
Advantages in a low-tech aquarium
- Hardy, versatile, and adaptable (no special substrate required).
- Red color without CO2 or added iron, as long as the lighting is adequate.
- Easy propagation: quick, affordable maintenance.
FAQ - Alternanthera cardinalis
Is CO2 needed to get a vivid red color?
No, but strong light enhances its color even more.
Can it grow in a low-tech setup?
Yes. It grows well without CO2, provided it gets enough light. It is not fussy about soil.
How should I prune it for a dense bush?
Cut off and replant the tops. The base will sprout again. Repeat to thicken the growth.
Why is my Alternanthera turning green?
Often due to insufficient lighting or a lack of iron (for example, if there are no fish): increase the light and add animals (fish, shrimp, microfauna). In rare cases, add an iron supplement.
Will goldfish eat it?
Some herbivorous fish may nibble on its fine leaves: use caution in tanks with these fish.
Additional information
- Scientific name: Alternanthera cardinalis
- Plant type: red stem plant
- Light: medium to high; its red color is enhanced by strong light.
- Temperature: 18 to 28°C. It cannot tolerate the cold: keep it in an aquarium, even an unheated one.
- Size: 30 to 50 cm in an aquarium (can grow above the water in an open-top tank).
- Packaging: 3 stems (approximate weight: 20 g).
- Guarantee: no rock wool or any kind of artificial substrate.
- 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.
