Alternanthera reineckii

Quick facts

Max height

40 cm

Growth rate

moderate

Difficulty

intermediate

Placement

midground, background

Propagation

stem cuttings

Water parameters

Temperature

22–28°C

pH

6.0 to 7.5

Hardness

1 to 15 dGH

Light and nutrients

Lighting

high

CO2

not required, but boosts growth and color

Substrate

nutrient rich

Feeding

feeds from both water column and roots (liquid ferts plus root tabs)

Substrate

What this plant roots into (or attaches to). The substrate affects both plant nutrition and water chemistry; see each linked page for full effects.

This plant feeds primarily from the water column, so substrate choice matters more for its fish-tank compatibility than for plant nutrition.

With fish

Plant-eating fish

will be eaten by mollies, silver dollars, large goldfish, and other plant-grazers

Diggers (corydoras, loaches)

may get uprooted by active diggers

Root-disturbing fish

sensitive to root disturbance, plant where roots stay undisturbed

Habitat

Native to South American river floodplains, where it grows primarily as an emersed (above-water) plant along muddy banks and in seasonally flooded areas. The species transitions to submerged growth when water levels rise, developing the deep red coloration that makes it popular in aquariums. Found across tropical South America from Argentina through Brazil. Several variants and cultivars exist in the aquarium trade: 'Mini', 'Rosanervig' (pink-veined), and the standard form. The emersed form is green to olive with reddish undersides; the submerged form develops intense red, purple, or magenta coloring under strong light. This is one of the most accessible red-leaved aquarium plants because it doesn't absolutely require CO2 injection, though color intensity improves dramatically with it. The genus Alternanthera includes many terrestrial species; only a few are truly aquatic.

Care notes

One of the few reliably red aquarium plants that doesn't demand CO2 injection, though it colors up much more vividly with CO2 and high light. Without CO2, expect brownish-red to burgundy rather than bright crimson. Under low light, the lower leaves drop and the stem becomes leggy and unattractive. Medium to high lighting (50+ PAR at substrate level) is the minimum for decent coloration. A nutrient-rich substrate or regular root tab supplementation helps because the plant is a moderate root feeder. Water column dosing of iron and micronutrients supports leaf color. Growth rate is moderate; trim and replant tops every 3-4 weeks to maintain bushy growth. The bottom portions of untrimmed stems become bare as lower leaves are shaded out. Propagation is by cuttings: cut the top 10–15 cm and replant directly into substrate. The cut stem usually produces side shoots. Avoid planting in deep shade behind taller plants; the red coloration requires direct light. CO2 at 20-30 ppm combined with high light produces the most intense color. In low-tech setups, place it directly below the light source and keep it trimmed short.

Further reading

• How to cycle a fish tank
• Water chemistry for fishkeepers: pH, GH, KH, and what they mean