Alternanthera cardinalis: 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 an aquascape. The tops of the leaves remain a little greener, while the undersides turn pink-red, creating very noticeable shades and gradients in a cluster.
Easy to grow successfully, it suits low-tech tanks and can be propagated endlessly from cuttings.
Why choose Alternanthera cardinalis?
- Its color becomes more intense red under strong light, creating instant contrast.
- Low-tech compatible: grows without CO2, and no fertilizer or specialized substrate is needed.
- Extremely easy to propagate from cuttings (cut and replant the tops, use stem sections, or layer horizontally).
- Background and midground: creates beautiful, dense, structured clusters.
- Hardy plant for beginners (simple substrate, very flexible water parameters).
- Very useful in aquascaping for creating focal points.
Growing tips (simple and effective)
- Lighting: medium to high (the stronger the light, the redder and more compact the plant).
- Substrate: plain sand is enough. If there are fish, shrimp, or other animals, no fertilizer is needed. The iron in their waste is enough, too.
- CO2: completely unnecessary in low-tech tanks. Fish and shrimp respiration also provides enough.
- Water 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. An aquarium plant, even in an unheated tank.
Use in aquascaping
- Creates striking contrast with green plant groupings. Its red color is nuanced and slightly metallic.
- Place it in the background to add depth, or in the midground to stand out against a green backdrop.
- Prune regularly for a dense cluster and a more compact shape. Remember to replant the cuttings!
Benefits 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: quick, economical maintenance.
FAQ - Alternanthera cardinalis
Is CO2 needed to get a vivid red color?
No, but strong lighting will intensify the color even more.
Can it grow in a low-tech tank?
Yes. It grows well without CO2 as long as it gets enough light. It is not fussy about the substrate.
How do I prune it to create a dense cluster?
Cut off the tops and replant them. The base will sprout again. Repeat to thicken the cluster.
Why is my Alternanthera turning green?
Often because of insufficient light or a lack of iron (for example, if there are no fish): increase the light and add animals (fish, shrimp, or microfauna). In rare cases, add an iron supplement.
Do goldfish eat it?
Some herbivorous fish may nibble on its delicate leaves, so be cautious in tanks with these fish.
Additional information
- Scientific name: Alternanthera cardinalis
- Plant type: red stem plant
- Lighting: medium to high; its red color is enhanced by light intensity.
- Temperature: 18 to 28°C. It does not tolerate cold; keep it in an aquarium, even an unheated one.
- Size: 30 to 50 cm in an aquarium (may grow above the water in an open tank).
- Pack: 3 stems (approximate weight: 20 g).
- Guarantee: contains no rock wool or artificial substrate of any kind.
- Recommendation: as a precaution, please never release this plant into the wild. It is not native to our region and should obviously not become established in the wild, but we must protect our ecosystems.
