Water sprite

Overview

Water sprite (Ceratopteris thalictroides) is a fast, forgiving fern with delicate, lacy green leaves — and one of the most flexible plants you can keep. Rooted in the substrate it makes a soft, feathery midground or background bush; floated at the surface it becomes a trailing nursery for fry and shrimp. It grows quickly, soaks up nutrients, and asks for very little, which makes it a classic first plant for a new or unstable tank that needs help finding its balance.

Planting & placement

Water sprite works planted or floating, and you can switch between the two freely. To plant it, bury only the base of the stem gently in the substrate, leaving the crown clear — burying the crown causes rot. To float it, just lay it on the surface and let the roots dangle. Because it grows tall and lacy, it is ideal for softening the midground and background; see how to plant aquarium plants for anchoring young stems, and aquascaping for beginners for placing it in a layout.

Light, CO2 & ferts

Give water sprite medium to high light for full, dense growth; in dim tanks it grows thin and reaches upward. It needs no CO2. As a fast grower it is a hungry plant, so a regular complete water-column fertilizer keeps the leaves bright green and stops them yellowing — our best fertilizer picks work well. Iron and nitrogen in particular keep the fine foliage lush.

Propagation & problems

Water sprite propagates itself generously: tiny plantlets form on the edges and tips of mature leaves, and once they have their own roots and leaves you can detach them and grow them on. Floating specimens tend to pump out plantlets fastest. The main issue is melt after planting — normal as the plant settles in — and thin, pale growth under weak light. Fix the light and keep it fed, and water sprite is an almost unkillable, endlessly renewable plant that pulls nutrients from the water and gives fry somewhere to hide.