Red Alternanthera (Alternanthera reineckii)

Choose Alternanthera reineckii for red contrast

Alternanthera reineckii is a South American stem plant and one of the most popular red plants for planted aquariums. Depending on the form and the light, its leaves range from brown-red and copper to cherry red and pink, often with a pinker underside. Planted as a group, it stands out sharply against green plants.

It belongs to the amaranth family, Amaranthaceae. A USDA weed risk assessment gives its native range as Brazil, Paraguay and Argentina, where it grows as an amphibious perennial along river courses, in seepage areas and in rain pools, both fully submerged and above the water. Wikipedia lists older names including Alternanthera cardinalis, Telanthera osiris and Alternanthera rosaefolia, and the USDA report records the common name temple plant.

Nurseries sell several named forms, such as 'Pink', 'Red', 'Mini', 'Rosanervig' and 'Lilacina'. This listing is sold as the species without a cultivar name, so the care below draws on the published profiles of the closest standard forms and says where they differ.

Decide from the complete growing picture

Tropica and Dennerle both rate it medium difficulty. That is the honest summary: it is not hard, but the colour that makes people buy it depends on good light and steady nutrients, so it suits a keeper who is ready to give it both. Our fish for planted aquariums collection lists peaceful species that suit this kind of planted set-up.

Select a bunch or a potted plant

Each purchase is one bunch of cut stems or one potted plant, chosen with the Format option. The number of stems and their colour vary with the growing season, and a plant grown in bright nursery conditions can look different once it settles in your aquarium. The photograph shows the plant, not the exact bunch or pot you will receive.

Prepare each format the right way

• Bunch: remove any band or weight, separate the stems and take the leaves off the part of each stem that will go into the substrate.
• Potted: take the plant out of its pot and remove as much of the growing material from the roots as you can, then split it into stems or small clumps.
• Either format: rinse in dechlorinated water and look for snails, eggs or other hitchhikers before planting.

Because the species grows both under and above water, nursery stock may have been grown with its leaves in the air. New underwater leaves can then look a little different from the ones the plant arrived with, and a few older leaves may drop while it adjusts. Judge the plant by its new growth.

Leaf colour also depends on light and nutrients, so the plant can look greener on arrival and redden as it settles in good light. Have the aquarium ready before you order; dispatch days and arrival times are on our delivery information page.

Plan the space around the grown stems

The published heights vary with the form. Tropica's 'Pink' grows stems 25–50 cm tall and averages 20–30 cm or more after two months; Dennerle's 'Red' reaches up to 40 cm; the USDA assessment, citing the Tropica catalogue, gives 15–50 cm tall and 10–15 cm wide for the species; Wikipedia gives up to 30 cm. Plan for a tall stem plant that you trim to the height you want.

Dennerle places it in the background, and Tropica recommends planting it in groups. A group in the midground or background shows the colour best. The compact 'Mini' cultivar, at 5–10 cm or more, is a separate foreground form and is not what this listing describes.

Use a three-step space check

1. Measure the depth from substrate to surface; stems that reach the surface need trimming.
2. Allow width for each plant, using the 10–15 cm spread from the USDA report as a guide, so the group is not crowded.
3. Check the sightline: place the group where green plants sit behind or beside it, so the red reads clearly.

To dose fertiliser accurately you need the aquarium's real volume. Our tank volume calculator works it out from the dimensions.

Give it the light and CO2 that bring out red

Light drives the colour. Tropica says good light encourages the leaves to turn red and rates the light demand of its Pink form as medium (it defines medium as about 0.5 W per litre). Dennerle rates its Red form high to medium and says the plant needs good lighting for the most intense colours. The Aquasabi aquascaping wiki explains that red leaves come from anthocyanins, pigments that protect the plant from strong light, so plenty of light is a prerequisite for a deep red.

CO2 helps. Tropica rates its demand as medium, which it defines as 6–14 mg/L; Dennerle gives 20–30 mg/l and says the plant needs an adequate supply. The sources differ by form, but both put it above the low-demand plants.

Match light, CO2 and nutrients to the colour you want

Nutrients need balance rather than excess. Aquasabi notes that when nitrate is high, the leaves of some plants turn green or brownish, and that limited nitrogen and phosphate bring out red, but it warns that an insufficient supply puts growth at risk. It also says iron is not needed to form the red pigment, although it is needed for chlorophyll; other growers recommend iron for red plants, so the sources disagree. The practical answer is a complete liquid fertiliser, a nitrate test before you add more, and no extreme dosing. If you keep shrimp, choose a fertiliser labelled as safe for them.

Keep the water within its range

Dennerle gives 22–28°C, pH 5–8 and soft to hard water for its Red form; Tropica publishes no water values for its Pink form. That means a heated tropical aquarium, and water that most UK taps supply. Hardness is rarely the problem; pH above 8 is outside the published range, so test it if you live in a very hard-water area.

Separate the plant's range from your fish's range

Your fish set the final targets. Compare the readings of your tap water and aquarium with your livestock using our water matcher, and read our water chemistry guide for what pH, KH and GH mean in practice.

Stable values matter more than perfect ones. Sudden changes in temperature or pH are more likely to make a newly planted stem drop leaves than a steady value at either end of the range.

Plant it and settle it in during the first week

Plant the stems singly, a short distance apart, so light reaches the lower leaves; a group of several stems looks better than a tight bundle. Push the bare lower part of each stem into the substrate deep enough that it stays put.

It is a rooted stem plant, so a nutrient-holding substrate gives it a good start, and a liquid fertiliser feeds the leaves through the water.

Use a first-week checkpoint plan

Some leaf loss in the first days can happen after a move, especially for plants grown above water. Remove dropped leaves so they do not decay in the tank, and keep conditions stable while the stems adjust.

Pinch, trim and propagate for a bushy group

Tropica says it is easy to propagate by nipping off the terminal bud and planting it in the substrate, and that this makes the mother plant bushier because it forms more side shoots. Dennerle lists head cuttings and side shoots, and advises trimming the stems every 6–8 weeks.

Make each cut count

1. Cut a stem just above a pair of leaves, a few centimetres below the tip.
2. Plant the cut tip in the substrate next to the group; it will root and grow into a new stem.
3. Leave the mother stem in place; new side shoots form below the cut.
4. When lower stems become bare, replace them with fresh tops rather than keeping long, leafless stems.
5. Net out every loose leaf and fragment, and dispose of surplus stems away from water.

Trimming on a regular cycle keeps the group dense and stops the tops from shading the lower leaves, which is the main reason stem plants become bare at the base.

Read the leaves and act early

Alternanthera reineckii shows its condition in its colour. Change one thing at a time and give each change a couple of weeks, because new leaves show the result, not old ones.

Pair each sign with an action

Algae grow on any plant under strong light when nutrients and light are out of balance. Our algae control guide explains the causes, and grazers such as Otocinclus and Amano shrimp help keep the leaves clean.

Pick tank mates that share 22–28°C

The plant's range defines the community: tropical, peaceful fish that like a planted tank. Small schooling fish look their best swimming in front of red stems, and algae grazers keep the leaves clean.

Good partners include the Zebra Oto, a small algae-grazing catfish (see our Otocinclus care guide), the Amano Shrimp, and small schooling fish such as the Cardinal Tetra, the Ember Tetra and Harlequin Rasboras. Check each species' own temperature range against the plant's before you buy. Dennerle also suggests it as a splash of colour among sword plants.

Screen companions with four questions

1. Do the temperatures overlap? The aquarium must stay within 22–28°C for the plant and within each fish's own range.
2. Does the fish eat or uproot soft plants? Large diggers and plant-eaters undo a red group quickly.
3. Will the group still have light? Floating plants and tall neighbours can shade it.
4. Is there an algae plan? Grazers help, but balanced light and nutrients come first.

More algae grazers are in our algae eaters collection.

Keep it out of ponds and the wild

Alternanthera reineckii is an aquarium plant. The USDA assessment found that it has naturalised in Taiwan, and that some of its close relatives, such as Alternanthera philoxeroides (alligator weed) and A. sessilis, are serious invaders. OATA advises that aquarium plants should never be used in ponds because of their potential to become invasive.

Dispose of trimmings safely

• Never rinse plants, trimmings or aquarium water into a sink, drain, pond, stream or river.
• Let surplus stems dry out, then put them in household waste or compost them well away from water.
• Follow the Be Plant Wise message that OATA supports: know what you grow, stop the spread, and compost with care.

For more easy plants to combine with it, read our live plants for beginners guide.

Answer Alternanthera reineckii buying questions

Why is my Alternanthera reineckii turning green?

Usually because it has too little light. Good light is what turns the leaves red. Very high nitrate can also leave some red plants greener or brownish, so test the water before adding more fertiliser.

Does Alternanthera reineckii need CO2?

It is not strictly required, but both growers rate its CO2 demand as medium or higher, and added CO2 gives the best growth and the strongest colour. Tropica gives 6–14 mg/L as its medium level; Dennerle gives 20–30 mg/l for the Red form.

How do I make it bushier?

Pinch off the top of each stem and replant it. The cutting roots, and the mother plant forms more side shoots, so the group fills out.

How tall does Alternanthera reineckii grow?

It depends on the form. Tropica gives 25–50 cm stems for its Pink form, Dennerle up to 40 cm for its Red form, and a USDA risk assessment 15–50 cm tall and 10–15 cm wide for the species. Trimming keeps it at the height you want.

Which form of Alternanthera reineckii is this?

This listing is sold as the species, Alternanthera reineckii, without a cultivar name. Leaf colour depends on light and nutrients, so plants can look greener on arrival and redden as they settle in good light.

What temperature and water does it need?

Dennerle gives 22–28°C, pH 5–8 and soft to hard water for its Red form. That means a heated tropical aquarium; most UK tap water suits it once its pH is within that range.

Is Alternanthera reineckii safe with shrimp?

Yes, provided the fertiliser is shrimp-safe. Rinse new plants and check them for snails before planting, and keep the filter intake guarded so small shrimp are not drawn in.

Should I choose the bunch or the potted plant?

The bunch gives you cut stems to plant straight away in a group. The potted plant arrives rooted in growing material, which you remove before planting. Both grow into the same plant.

Consult the plant references

• Tropica: Alternanthera reineckii 'Pink' — difficulty, growth rate, light and CO2 demand, stem height, pink leaf undersides, group planting and propagation by pinching out the tip.
• Dennerle Plants: Alternanthera reineckii 'Red' — light, CO2, height, temperature, pH, hardness, placement, propagation and the 6–8 week trimming interval for the Red form.
• Tropica: Alternanthera reineckii 'Mini' — the compact Mini cultivar and its 5–10+ cm height, for comparison.
• USDA APHIS: Weed Risk Assessment for Alternanthera reineckii (2016) — native range, amphibious habit, height and width, synonyms, naturalisation in Taiwan and its invasive relatives.
• Wikipedia: Alternanthera reineckii — family, native habitats and older synonyms.
• Aquasabi aquascaping wiki: How will my aquatic plants turn properly red? — how light, nitrate and iron affect red leaf colour.
• OATA: Aquatic plants and Be Plant Wise — UK trade guidance that aquarium plants should not be used in ponds, the Be Plant Wise campaign and safe disposal.
• Tropical Fish Co delivery page — current dispatch days and arrival times.