Asian Watermoss

Buy a small portion of this and you will be scooping handfuls out within the month. That is the point of it: Salvinia cucullata grows fast enough to pull meaningful quantities of nitrate and phosphate out of the water column and lock them into leaf tissue you physically remove at each water change. As a nutrient export tool in an over-fed tank it does more real work than most stem plants.

The leaves are what separate it from the commoner Salvinia natans. Each floating leaf is cupped into a hood (cucullata means hooded), so an established mat reads as a field of small green pockets rather than flat paired ovals. Dense water-repellent hairs on the upper surface keep the leaf dry. There are no true roots anywhere on the plant; a third, finely divided leaf hangs beneath each node and does the absorbing.

Care is mostly a matter of restraint rather than provision. It settles at 24 to 28 °C and tolerates pH 5 to 8 across soft and moderately hard water, so chemistry is rarely the limiting factor. Injected CO2 does nothing for it, since it takes carbon from the air above the waterline. The two things that actually kill it are surface agitation, which wets the leaves and rots them, and neglect, which lets the mat thicken until nothing below gets light.

Thin it weekly once it establishes. Daughter plants form along the horizontal stem and separate without help, so a single fragment carrying one node will rebuild a colony.