Alternanthera cardinalis: red and easy plant for natural aquariums
A red plant that brings contrast
Alternanthera cardinalis is one of the best plants to bring red and depth to a layout. The top of the leaves remains a bit greener, while the underside turns pink-red, creating very visible shades and gradients in a bush.
Easy to succeed, suitable for 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 technical substrate needed.
- Ultra-simple propagation (cut and replant tips, cuttings, horizontal layering).
- Background and middle: creates beautiful dense and structuring bushes.
- Robust plant for beginners (simple substrate, very flexible parameters).
- Very valuable in aquascaping to create focal points.
Growing tips (simple and effective)
- Light: medium to strong (the stronger, the redder and more compact).
- Substrate: simple sand is enough. With fish, shrimp, or other animals present, no fertilizer needed. The iron in their waste is also sufficient.
- CO2: completely unnecessary in low-tech. In fact, fish or shrimp respiration provides enough.
- Parameters: fresh to moderately hard water. A truly tolerant plant if the water is not extreme.
- Size: cut above a node and replant the tip; the base will produce new shoots.
- Temperature: does not survive winter outdoors. Aquarium plant, even unheated.
Use in aquascaping
- Strong contrasts with green masses. Nuanced red, slightly metallic.
- Background placement to give depth, or in the middle to stand out on a green background.
- Regular trimming for a dense bush and a more compact silhouette. Remember to replant the cut parts!
Advantages in low-tech aquariums
- Resistant, versatile, and adaptable (no technical substrate required).
- Red color without CO2 or added iron if lighting is sufficient.
- Easy propagation: economical and quick maintenance.
FAQ - Alternanthera cardinalis
Is CO2 needed to get bright red?
No, but strong light further enhances the color.
Can it live in low-tech setups?
Yes. It grows well without CO2, provided there is enough light. The substrate does not matter much.
How to trim it for a dense bush?
Cut and replant the tops. The base will sprout. Repeat to thicken the cluster.
Why is my Alternanthera turning green?
Often insufficient lighting or lack of iron (for example, in the absence of fish): increase light and introduce animals (fish, shrimp, microfauna). In rare cases, add an iron supplement.
Do goldfish eat it?
Some herbivorous fish may nibble its thin leaves: be cautious in affected tanks.
Additional information
- Scientific name: Alternanthera cardinalis
- Plant type: red stem plant
- Light: medium to strong, its red color is enhanced by light intensity.
- Temperature: 18 to 28°C. It does not tolerate cold: reserved for the aquarium, even if unheated.
- Size: 30 to 50 cm in aquarium (can emerge in an open tank).
- Packaging: 3 stems (approximate 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 naturalize, but we must protect our ecosystems.
