Downoi

Quick facts

Max height

10 cm

Growth rate

moderate

Difficulty

intermediate

Placement

foreground, midground

Propagation

lateral shoots

Water parameters

Temperature

22–28°C

pH

5.5 to 7.5

Hardness

2 to 15 dGH

Light and nutrients

Lighting

high

CO2

required for healthy growth

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

safe with plant-eating fish (tough leaves or unpalatable)

Diggers (corydoras, loaches)

may get uprooted by active diggers

Root-disturbing fish

tolerates fish that disturb roots

Habitat

Native to Thailand, found growing along stream banks and in shallow water in northern Thailand. The species (Pogostemon helferi) is commonly called 'downoi' (the Thai word for star) because of its distinctive star-shaped leaf rosettes. Each leaf is wavy-edged, bright green, and emerges in a zigzag pattern from a compact rosette, creating a layered, ruffled appearance unlike any other aquarium plant. The rosettes are 3–8 cm in diameter and 3–6 cm tall, making the plant suitable for foreground to midground use. Discovered for the aquarium hobby in the early 2000s during a collecting trip along the Thailand-Myanmar border, P. helferi quickly became a sought-after species for its unique form. The common name 'downoi' has stuck in international aquascaping despite being a Thai word, reflecting the species' initial introduction through Thai aquarium plant collectors. The plant was quickly adopted by the Nature Aquarium movement and featured prominently in early ADA (Aqua Design Amano) aquascaping publications, cementing its status as a classic aquascaping species.

Care notes

Moderate to demanding. Requires moderate to high light and benefits strongly from CO2 injection. Under low light or without CO2, the rosettes become elongated and lose the compact, star-shaped form that is the plant's appeal. Rich substrate is important: the plant is a vigorous root feeder and develops a substantial root system. Root tabs and nutrient-rich substrate (aquasoil) produce the best results. Iron and potassium are particularly important; deficiency shows as pale new leaves or loss of the ruffled leaf texture. Plant individual rosettes 3–5 cm apart. Growth is moderate; the plant produces new rosettes on short runners, gradually forming a cluster of overlapping stars. Temperature: 22–28°C. pH 6.0-7.5. Soft to moderately hard water. The zigzag, ruffled leaf pattern catches light at multiple angles, creating a visually complex texture that adds depth to the foreground. Propagation by separating daughter rosettes from runners. The plant can also produce small plantlets from the leaf axils. A unique and eye-catching foreground plant for medium to high-tech setups.

Further reading

• CO2 injection for planted tanks: what it costs, what it does, and when to skip it
• Water chemistry for fishkeepers: pH, GH, KH, and what they mean