Rootless duckweed

Wolffia arrhiza is a tiny floating flowering plant with a simplified, rounded body and no roots. It occurs in sheltered standing water and often grows alongside duckweeds. Its very small size makes it easy to carry into an aquarium with other surface plants, but it can also be maintained deliberately as a floating plant.

It is a fast-growing surface species. Keep water at 20 to 28 °C and pH 5 to 8, with light ranging from low to high. A small starting portion may spread substantially when conditions suit it, but neither the time to establish nor the time to cover a tank is fixed. It is not planted into the substrate; keep the floating bodies at the surface where they receive light.

The main maintenance decision is how much surface cover the layout can accommodate. Remove excess before it shades the plants beneath or crowds other floaters, and check filters and container edges for leftover fragments. Propagation is by division of the floating population. Small remaining portions can restart growth, so a single skimming may not remove it completely. Do not rely on this plant to make a stocked aquarium safe during cycling: filtration and water-quality checks remain necessary.