Hydrocotyle sp. "Japan"

Geographical Origin and Habitat: This plant, also known as Hydrocotyle tripartita, comes from Australia and the subtropical regions of Asia. In nature, it colonizes the damp banks of streams, river shores, and marshy areas subject to flooding. It made its entry into the aquascaping hobby through Japanese channels (hence the trade name 'Japan'), where it was appreciated for its extraordinary ability to creep and climb on wet surfaces.

Taxonomy & Genetics: Placed in the family Araliaceae, this form is considered a compact-growing and small-leaved variant of Hydrocotyle tripartita. Although a separate botanical species has not yet been described, the plant stably maintains its small leaf size and marked branching tendency in submerged culture. Its genetics allow for extraordinarily rapid growth rates under optimal stimuli.

Physical Structure: It features a very thin creeping stem (stolon) that propagates in all directions. From each node of the stem, tiny roots and petioles develop, bearing a single leaf. The leaf has a very characteristic tripartite shape, deeply divided into three distinct lobes (hence the scientific name tripartita). Under strong light, the stems tend to bend downward, intertwining to form a dense carpet.

Color & Texture: The color is an intense and bright emerald green, extremely fresh and lively. The leaf texture is soft and delicate, and the leaves appear translucent under aquarium lighting. The tiny size of the leaves (often less than 1 cm in diameter) makes it ideal for creating a sense of microscopic scale and naturalness in nano aquariums or complex layouts.

Lighting & CO2: Although it can survive in moderate light, it requires intense lighting and a constant supply of CO2 (15-25 mg/l) to remain compact and creep along the substrate. If the light is weak, the plant responds by stretching vertically and climbing on neighboring plants or decor in a messy way.

Nutrition & Substrate: It is a fast consumer of nutrients, particularly iron, potassium, and nitrogen. It benefits greatly from regular liquid fertilization in the

Water Chemistry: Tolerates a wide spectrum of chemical conditions. The ideal pH is between 5.5 and 7.5, with soft to moderately hard water. The tolerated temperature ranges from 10°C to 30°C, making it suitable even for cold-water tanks or outdoor summer cultivation in Wabi-Kusa bowls.

Space Management & Placement: Extremely versatile. It can be planted in the foreground to create a carpet, inserted in the midground to climb rocks and wood, or even wedged into hardscape crevices as a temporary epiphyte plant. Its rapid growth requires constant space monitoring.

Pruning: Pruning must be done regularly to prevent the carpet from becoming too thick and the lower part from rotting due to lack of light. It is pruned simply by shearing the bush with wavy aquascaping scissors. Cut parts root with extreme ease if replanted or left floating on the bottom.

Risks & Diseases: The main risk is that the plant becomes invasive, invading space intended for slower species. Also, due to its dense and intricate growth, it can accumulate organic debris between the stems, attracting filamentous algae if water flow and the presence of cleaning shrimp are not adequate.