How do you grow Alternanthera reineckii in an aquarium? Plant the stems in nutrient-rich substrate, give medium to strong light and add CO2 for the best red color. Dennerle lists 72 to 82°F (22 to 28°C), pH 5 to 8 and 20 to 30 mg/L CO2 for Alternanthera reineckii ‘Red’. Tropica’s compact ‘Mini’ form can be trimmed into a red-violet carpet 2 to 4 inches (5 to 10 cm) tall.
Key takeaway: Alternanthera reineckii is a red stem plant from South America in the amaranth family. Its color depends on light, CO2 and nutrients. Dennerle lists strong to medium light, 20–30 mg/L CO2, 72–82°F (22–28°C) and propagation by tip cuttings and side shoots. Tropica’s ‘Mini’ cultivar stays 2–4 in (5–10 cm) tall and can form a dense foreground carpet with careful trimming.
| Fact | What sources report | Source |
|---|---|---|
| Family and origin | Amaranthaceae; South America | Dennerle |
| Height | ‘Red’ up to about 20 in (50 cm); ‘Mini’ 2–4 in (5–10 cm) | Dennerle, Tropica |
| Light | Strong–medium (Dennerle); medium (Tropica ‘Mini’) | Dennerle, Tropica |
| CO2 | 20–30 mg/L (Dennerle); medium need (Tropica) | Dennerle, Tropica |
| Temperature | 72–82°F (22–28°C) | Dennerle |
| pH and hardness | pH 5–8; soft to hard | Dennerle |
| Propagation | Tip cuttings and side shoots | Dennerle |
What Is Alternanthera Reineckii?
Alternanthera reineckii is an aquatic stem plant in the amaranth family (Amaranthaceae), native to South America according to Dennerle. Dennerle calls the ‘Red’ form a real plant classic in red, used in the background of larger tanks. It grows up to about 20 inches (50 cm), with lance-shaped leaves that are pink to deep red on top and wine-red underneath.
Several cultivars are sold. Tropica’s ‘Mini’ is a compact form with slower growth that suits small tanks and foregrounds, and growers also see ‘Rosaefolia’ and ‘Lilacina’. In nature the plant often grows emersed, as in the photos here, and it shifts to its softer, redder underwater leaves after planting.
- ‘Red’: tall background stems.
- ‘Mini’: compact foreground or midground bush.
- Use: a red accent among green plants such as Rotala.
How Do You Grow Alternanthera Reineckii in an Aquarium?
Plant individual stems a short distance apart in nutrient-rich soil or substrate with root tabs. Strip the lower leaves and push each stem about 1 to 2 inches (2.5 to 5 cm) deep with tweezers. Give space between stems so light reaches the lower leaves; crowded stems lose leaves at the bottom.
- Remove rock wool and lower leaves from each stem.
- Plant stems one by one, about 1 inch (2.5 cm) apart.
- Place ‘Red’ in the background and ‘Mini’ in front.
- Start lights at 7–8 hours a day to limit algae while it settles.
- Expect some old leaves to drop as it adapts to water.
What Light Does Alternanthera Reineckii Need?
Give it medium to strong light. Dennerle rates the light need of the ‘Red’ form as strong to medium, and Tropica rates the ‘Mini’ as medium but says high light and CO2 improve growth and appearance. Under weak light it turns greenish-brown and drops lower leaves; under good light the red deepens.
Keep the photoperiod moderate, around 7 to 8 hours, and raise intensity rather than hours. Fast algae on slow-growing red plants is a sign of too much light for the CO2 and nutrients in the tank.
Does Alternanthera Reineckii Need CO2 and Fertilizer?
It grows best with both. Dennerle lists 20 to 30 mg/L CO2 and says that, as with all red-leaved stem plants, good lighting, enough CO2 and a good supply of nutrients through the water column are especially important. Tropica rates the ‘Mini’ as medium for CO2. Without CO2 the plant survives in some tanks but colors poorly.
- CO2: 20–30 mg/L for strong color; see aquarium CO2 for plants.
- Liquid fertilizer: dose regularly; see aquarium plant fertilizer.
- Root tabs: help in inert sand or gravel; see aquarium root tabs.
- Iron: supports red pigment in new growth.
What Water Parameters Does Alternanthera Reineckii Like?
Keep the tank warm and stable. Dennerle lists 72 to 82°F (22 to 28°C), pH 5 to 8 and soft to hard water for the ‘Red’ form. That range fits most tropical planted tanks. Stable CO2 and nutrients matter more for color than small changes in pH or hardness.
- Temperature: 72–82°F (22–28°C).
- pH: 5–8.
- Hardness: soft to hard.
How Do You Trim and Propagate Alternanthera Reineckii?
Cut the tops and replant them. Dennerle lists tip cuttings and side shoots as the propagation methods. When stems reach the surface, cut the top 3 to 4 inches (8 to 10 cm) and replant them in front of the old stems, which will branch below the cut. Tropica says careful trimming of the ‘Mini’ creates a dense, red-violet carpet about 2 to 4 inches (5 to 10 cm) tall.
- Cut stems just above a leaf pair with sharp scissors.
- Replant the healthy tops between older stems.
- Remove bare, leggy bottoms if the group looks thin.
- Trim the ‘Mini’ lightly and often to keep it low.
Why Is Alternanthera Reineckii Melting or Losing Color?
The common causes are emersed-to-submerged transition, low light, low CO2 and nutrient shortages. Nursery plants are often grown out of water, so some leaves melt after planting. Green or brown leaves point to weak light or CO2, while holes and pale new growth point to nutrients. Fix light and CO2 first, then dosing.
- Leaves melting after planting: normal adaptation; trim and wait.
- Green instead of red: more light or CO2 needed.
- Lower leaves dropping: stems too crowded or light too weak.
- Pale, small new leaves: feed more iron and macronutrients.
FAQ About Alternanthera Reineckii
Does Alternanthera reineckii need CO2?
It grows best with it; Dennerle lists 20–30 mg/L.
How tall does the plant get?
The ‘Red’ reaches about 20 inches (50 cm); ‘Mini’ stays 2–4 inches (5.1–10 cm).
Why is my Alternanthera turning green?
Usually too little light or CO2.
Can it grow emersed?
Yes; nursery plants are often grown emersed.
How do you propagate it?
From tip cuttings and side shoots.
What temperature does it need?
72–82°F (22–28°C), per Dennerle.
Sources
- Dennerle Plants — Alternanthera reineckii ‘Red’ plant profile/22974)
- Tropica Aquarium Plants — Alternanthera reineckii ‘Mini’ plant info
- Photo credits (Wikimedia Commons, edited with titles): Alternanthera reineckii ‘Roseifolia’ 2023-07-30 01 by Agnieszka Kwiecień, Nova (CC BY-SA 4.0); Alternanthera reineckii ‘Liliacina’ kz01 by Krzysztof Ziarnek, Kenraiz (CC BY-SA 4.0)
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