Hygrophila corymbosa ''Red''

Geographic Origin and Habitat: A botanical variety cultivated and selected in aquarium greenhouses (often labeled commercially as "Red", "Ozelot", or "Kompakt Red"), descending directly from Asian populations of *Hygrophila corymbosa*. Its wild ancestors inhabit the swamps and edges of monsoon rivers in Southeast Asia, but this specific pigmented cultivar is an exclusive product of ornamental horticulture, optimized to provide vivid chromatic contrasts in Dutch-style tanks.

Taxonomy and Genetics: A dicotyledon of the Acanthaceae family. It shares the same genetic makeup as the green form, but presents a strong genetic tendency to produce anthocyanins (red and purple pigments) as a cellular photoprotection mechanism when exposed to high light intensities. Unlike the 'Angustifolia' form, the leaf blades are broader, ovoid, and end in a point.

Physical Structure: It possesses a fleshy stem, lignified at the base in adult plants, capable of supporting the entire architecture of the plant. Roots are abundant both at the substrate level and as adventitious filaments emerging from intermediate nodes. The leaves are large (8-12 cm long), decussate, and arranged in a rosette on the apical nodes, forming compact and spectacular "heads".

Color and Texture: Color is the true spectacle of this cultivar. The base of the leaf and the shaded parts maintain an olive green tone. Moving closer to the apex or under direct light, the leaf blades ignite with brick red, bright bronze, dusty pink, and burgundy, crossed by obvious lighter or yellowish veins. The underside of the leaf often takes on a distinct silvery-purplish reflection. The texture is robust and slightly crinkled.

Lighting and CO2: Unlike the green varieties, this cultivar "demands" intense lighting (PAR > 60-80) to trigger and maintain its beautiful red hues. Under dim light, the plant will not die, but it will turn green, completely losing its charm. CO2 injection (20-30 mg/l) is not strictly mandatory, but is highly recommended to encourage the full expression of colors and a massive leaf diameter.

Nutrition and Substrate: Extremely greedy for macronutrients. It requires a rich and porous substrate from which to absorb structural elements. To maximize red colorations, it is common practice in planted aquariums to slightly lower the nitrates in the water column (nitrogen limitation stress) and simultaneously administer generous doses of trace elements and chelated divalent Iron.

Water Chemistry: Relatively plastic, but it prefers slightly acidic or neutral water (pH 6.5-7.2) and a medium-low KH (4-8) to facilitate the absorption of chelated iron. It tolerates tropical temperatures well (22-27°C). Regular water changes are vital, as the plant halts its growth and colors fade if the water becomes saturated with inhibitory substances.

Space Management and Placement: Its imposing size and broad leaves make it a quintessential "Dutch Street plant" (a plant used to create the classic ascending Dutch streets) or an extraordinary focal plant (centerpiece) for the midground or background in large tanks. The stems should be planted in a "staircase" fashion, from the lowest in front to the highest in back.

Trimming: Compared to the vigorous *H. polysperma*, it grows more slowly and majestically. To keep it bushy and compact, the apices must be vigorously topped when they reach the water surface. By cutting the red apical bud and replanting it, you not only propagate the plant but also force the older stem below to branch out, creating a dense bush of purple leaves.

Risks and Diseases: Like all Hygrophilas, it suffers irreparably from Potassium (K) deficiency, manifesting holes on the lowest leaves. Furthermore, due to its size and its propensity to extract nutrients, it can enter into ruthless competition with neighboring small carpeting plants, completely shading them with its broad apical rosettes.