Pistia stratiotes (Water Lettuce)

Pistia stratiotes, Water Lettuce, is a pantropical free-floating aquatic plant that forms rosettes of soft, velvety, pale-green leaves with distinctive parallel ribbing and a spongy air-filled texture that keeps it afloat. Its trailing feathery white roots hang 10–20 cm into the water column, absorbing nutrients and providing a refuge for small fish and invertebrates. Water Lettuce is one of the most effective nutrient-exporting plants available for paludariums with open water sections.

It thrives in warm, still or slow-moving water with high light and good humidity above the surface — conditions readily achieved in enclosed paludariums. It multiplies rapidly by producing offsets on short stolons, and unchecked growth can quickly cover an entire water surface. Regular harvesting keeps populations manageable and removes the nutrients the plant has absorbed from the water.

Light: High; 3,000–8,000 lux; insufficient light results in small, pale, stunted rosettes. CO2/Humidity: No CO2; humidity above the water surface should ideally exceed 70% for the best leaf development. Fertilisation: No fertilisation needed; absorbs all required nutrients directly from the water column. Placement: Float freely on the water surface; keep water movement gentle to prevent leaves from staying wet and rotting. Propagation: Remove and replant offset rosettes produced on stolons; extremely prolific under good conditions.