Hygrophila polysperma: the plant that grows in anything
It ships well, roots in a day, grows in low light without CO₂, and starts cleaning your water almost immediately. There is a reason it is in every fish shop in the world.
Where it comes from
Hygrophila polysperma — often called dwarf hygro or Indian waterweed — is native to South and Southeast Asia, with the broadest natural distribution from India across to Thailand and Malaysia. It grows in ponds, rice paddies, drainage ditches, and slow rivers, typically in shallow water with full sunlight. Its ecological success across this range comes from the same traits that make it popular in aquaria: it grows fast, tolerates a wide range of conditions, and competes aggressively for nutrients.
It has been introduced and naturalised in parts of North America, Central America, and Europe, where its fast growth allows it to outcompete native vegetation. It is on the Federal Noxious Weed list in the United States — meaning possession and transport across state lines is prohibited — though enforcement in the hobby context is inconsistent. In the UK it is legal to keep but should not be released into the wild.
What to expect
The standard form produces light to mid-green oval leaves, 2–4 cm long, in opposite pairs on pale green stems. Internodes are short in good light and longer in low light. The plant grows upright and stems can reach 30–50 cm in a tall tank before they begin to trail sideways at the water surface.
Hygrophila polysperma 'Rosanervig' is a distinctive cultivar with white-veined leaves that develop pink and reddish tones under high light. The variegation — white veins against a pale to medium green leaf — is caused by reduced chlorophyll in the vein tissue itself, which gives the veins their pale white appearance. It grows more slowly than the standard form and requires more light for the full variegated effect, but is otherwise equally tolerant.
The plant flowers readily when stems reach the water surface — small, pale lilac flowers emerge in the leaf axils of emersed growth.
How to keep it
| Parameter | Value |
|---|---|
| Lighting | Low to high — grows in virtually any aquarium light; compact growth in medium to high light |
| CO2 | Not required; growth is fast even without it |
| Temperature | 18–30°C — one of the widest ranges of any commonly kept aquarium plant |
| pH | 5.5–8.5 |
| Hardness | Soft to very hard — tolerates almost any tap water |
| Fertiliser | Not required for basic growth; regular dosing improves speed and leaf quality |
| Substrate | Any — grows in gravel, sand, or aquasoil; even thrives in bare-bottom tanks temporarily |
| Growth rate | Very fast — needs trimming every 1–2 weeks under good conditions |
| Placement | Midground, Background |
| Difficulty | Easy |
Why it is the best new-tank plant
In a cycling or recently set up tank, H. polysperma starts absorbing ammonia and nitrate from the water column within days. It needs no CO2, tolerates the parameter swings of a new tank, and produces visible new growth that reassures new hobbyists that something is working. The fast growth also means trimmed stems can be removed to physically export nutrients — reducing the nitrogen load before the filter matures. No other widely available plant matches this combination.
How to propagate
Cut stems to desired length (10–15 cm is ideal), remove the lowest 2–3 pairs of leaves, and plant the cut end in substrate. Roots develop within 24–48 hours in warm water — faster than almost any other stem plant. The cut parent stem will branch within a week, typically producing 2–4 new shoots.
Stems also root where they contact substrate, so a plant that has fallen or trails sideways will develop roots along its length and can be cut into multiple self-sufficient sections.
What goes wrong
Leggy growth with wide internodes. Insufficient light — the plant is stretching upward to reach more light. Move to a brighter position or trim the top and replant. In low light it will grow upward rather than stay compact.
Lower leaves yellowing and dropping. Normal in aging stems that have grown tall enough for the lower portion to be shaded. Regular trimming and replanting fresh cuttings maintains density. This is structural rather than a nutrient problem in most cases.
Rosanervig losing variegation. The pink and white variegation fades in low light. The Rosanervig form needs noticeably more light than the standard form to maintain its colour. Increase light intensity and trim regularly — new growth emerging in better light will show the full pattern.
Fish eating it. Goldfish, silver dollars, Buenos Aires tetras, and many cichlids will eat H. polysperma. Despite its fast growth it cannot regenerate fast enough to survive sustained herbivory. In plant-eating fish tanks, use harder plants (Java fern, Anubias) instead.
More plants in this series
- Water wisteria (Hygrophila difformis) — the shape-shifting stem plant
- Bacopa caroliniana — slow, lemon-scented, low maintenance
- Hornwort (Ceratophyllum demersum) — the fast-growing water purifier
- Vallisneria spiralis — the original background plant
- Rotala rotundifolia — the colour-shifting stem plant