Water lettuce

Overview

Water lettuce (Pistia stratiotes) is a striking floating plant — pale green rosettes of soft, ribbed, velvety leaves that sit on the surface like little floating lettuces, trailing long feathery roots beneath. Like other fast floaters it soaks up nutrients, shades the tank and helps starve algae, while those dense roots make excellent cover for fry and shrimp. It is easy and fast, with two things to manage: keeping the leaves dry, and thinning it before it takes over the surface.

Planting & placement

Water lettuce is not planted — it floats on the surface with its roots hanging free. It appreciates an open top with headroom, since the rosettes grow upward as well as out and dislike being squashed against a lid. Filter flow pushes floaters around, so pen it behind a floating ring or airline if you want it contained. Leave open surface for gas exchange and feeding. It needs no substrate; those long roots are prime fry habitat — see aquascaping for beginners for working floaters into a scape.

Light, CO2 & ferts

Give water lettuce medium to high light for large, healthy rosettes; it grows in less but stays small and pale. It needs no CO2, taking carbon from the air. As a fast grower it feeds heavily from the water column and is a strong nutrient sponge — a regular water-column fertilizer keeps it green, and its appetite for nitrate is what helps hold algae back.

Propagation & problems

Propagation is automatic: water lettuce sends out runners that produce daughter rosettes, which detach and spread, so a few plants become a full mat quickly. The main problems are centre rot from wet leaves and its own vigour — a thick mat blocks light to your rooted plants and gas exchange at the surface. Thin it often, scooping out and discarding the excess. Kept fed, dry-leaved and controlled in an open-topped tank, water lettuce is one of the most handsome and effective floating plants available.