Hygrophila polysperma

Hygrophila polysperma is native to the shallow, slow-moving waters and flooded fields of India and Southeast Asia, where it grows prolifically in warm, nutrient-rich environments. It is considered one of the easiest aquarium plants in existence, capable of surviving conditions that would kill most other aquatic plants — fluctuating pH, hard tap water, low light, and even minimal water movement. In the aquarium hobby it has been a staple for over a century, introduced early in the modern era of fishkeeping as a reliable green plant for community tanks. Its small, paired leaves range from bright green to reddish-pink under high light, and the variety 'Rosanervig' features striking pink venation. Despite its ease, Hygrophila polysperma grows at an impressive rate and can quickly dominate a tank if left untrimmed, making regular maintenance important. It is extremely effective as a biological filter supplement, consuming nitrates and phosphates rapidly. The plant is classified as invasive in parts of the southern United States where it has escaped into waterways, so proper disposal of trimmings is essential.

Placement Versatile — suitable for background, midground, or even foreground in larger tanks. Best planted in groups of 4–8 stems. Can be floated temporarily as a nutrient sponge in new aquariums.

Lighting Survives under very low light but grows best with moderate lighting (30–60 PAR). Under high light, some specimens develop reddish-pink coloration. A basic fluorescent strip lamp is sufficient for survival.

CO2 & Fertilisation CO2 injection is optional. The plant makes good use of nutrients already present in the water from fish waste. A minimal fertiliser dose once weekly is sufficient in most tanks.

Propagation Stem cuttings of any length above 5 cm will root readily. Simply insert cut stems into substrate. Side shoots are produced prolifically. One of the easiest plants to propagate in the entire hobby.

Trimming Trim every 2–3 weeks during active growth. The plant can grow 5–10 cm per week in warm, well-lit tanks. Trim back hard to keep it in check; it recovers rapidly. Dispose of trimmings responsibly — do not release into natural waterways.