Alternanthera reineckii 'Grün' ('Green')

Geographical Origin and Habitat: Alternanthera reineckii 'Grün' is native to the tropical and subtropical regions of South America, particularly within the Amazon basin, extending through Brazil, Paraguay, and Argentina. In the wild, this species typically colonizes muddy riverbanks, marshlands, and temporarily flooded soils, growing in both emersed and submerged states. Its natural habitat is characterized by soft, warm, and nutrient-rich waters where direct or partial sunlight stimulates vigorous growth and branching.

Taxonomy & Genetics: Taxonomically, it belongs to the Amaranthaceae family and the genus Alternanthera. The cultivar 'Grün' (or 'Green') is a variant specifically selected for its predominantly green foliage, which stands out from the more common red and purple cultivars such as 'Rosaefolia' or 'Mini'. Genetically, it retains the robustness of the wild type but exhibits reduced anthocyanin pigment synthesis under normal light levels, making it an excellent choice for aquascaping layouts focused on green gradients.

Physical Structure: It presents as a classic erect stem plant with opposite and decussate leaves. The stems are relatively thick and fleshy, capable of keeping the plant upright even in moderate currents. The leaves are lanceolate-ovate with slightly wavy margins and can reach lengths of 5-10 cm. The root system is fibrous and highly developed, anchoring firmly into the substrate to absorb nutrients.

Color & Texture: Unlike the red varieties, the upper side of the leaf is a bright green, ranging from apple green to olive green. However, the underside often retains subtle shades of pale pink, yellow-green, or purple, especially under high light. The leaf texture is soft yet elastic, featuring a prominent central vein that adds depth and definition to the leaf surface.

Lighting & CO2: It requires moderate to high lighting to thrive and prevent the internodes from stretching too far. While CO2 injection is not strictly mandatory, it is highly recommended to encourage compact and robust growth, with ideal concentrations between 15 and 25 mg/L. Under weak light, the plant tends to shed its lower leaves and decline.

Nutrition & Substrate: A nutrient-rich substrate, such as a premium aquasoil, is crucial to support the plant's extensive root system. It responds exceptionally well to

Water Chemistry: It prefers soft to moderately hard water, with a KH range of 0 to 14 dKH and a slightly acidic to neutral pH (5.0-7.0). It is highly adaptable regarding temperature, tolerating a wide range from 4°C to 30°C, though the optimal range for aquarium keeping is between 22°C and 26°C.

Space Management & Placement: Given its potential height of 40 cm, it is ideal for the midground or background of the aquarium. It should be planted in small groups of individual stems spaced about 2-3 cm apart to ensure adequate light penetration to the lower leaves. Avoid placing it in deep shade under hardscape or larger plants.

Pruning: Pruning is performed by cutting the main stem just above a leaf node. The topped portion can be replanted into the substrate to propagate, while the remaining bottom portion will quickly produce new lateral shoots, resulting in a bushier and more compact appearance.

Risks & Diseases: It is susceptible to green spot or thread algae if nutrients are imbalanced or if water flow is inadequate. The tender leaves can also be targeted by herbivorous fish or hungry shrimp; potassium deficiency is a common risk, showing as small pinholes in older leaves.