Propagating Ceratopteris cornuta (Horned Water Sprite)

How to multiply Ceratopteris cornuta using adventitious daughter plantlets that form on the leaf margins, plus simple division of this fast-growing floating fern.

Overview

Ceratopteris cornuta is a tropical fern in the genus Ceratopteris that may be grown as a floating (natant) plant or immersed and rooted in the substrate. It carries broad, membranous lobed fronds and a short, fleshy rhizome with stipes full of longitudinal air canals that keep it buoyant. Under bright light it grows fast enough to help cycle a new aquarium, and its dangling roots draw excess nutrients from the water column.

Because the species reproduces readily on its own, propagation is mostly a matter of harvesting the young plants it produces rather than forcing it. This makes it an ideal beginner fern for filling surface space and shading the tank below.

Propagation Method

Ceratopteris multiplies vegetatively through adventitious daughter plantlets: small plants form on the mother frond and are released once they are ready. The fronds also carry proliferous buds in the leaf axils that develop into new plantlets. A second, more deliberate route is division of an established clump, which simply splits the existing plant into independent pieces.

Adventitious plantlets on the leaf margins and frond axils (the main route).
Division of a large floating mat into smaller rooted sections.

Step-by-Step

Let a healthy parent plant grow under bright light until daughter plantlets appear along the leaf margins and in the leaf axils.
Allow each plantlet to develop its own small fronds and dangling roots while still attached to the mother frond.
Detach the plantlet gently once it is rooted and self-supporting; mature ones often release on their own.
Float the new plantlet on the surface, or to divide instead, pull a large mat apart into clumps that each retain roots.
Keep the new plants under good light and stable conditions until they establish and resume fast growth.

Conditions for Healthy Growth

Provide medium to bright lighting; the brighter the light, the faster Ceratopteris grows and the more freely it produces plantlets. It tolerates a wide range of soft to moderately hard water and does not require CO2 to thrive, though it responds well to extra nutrients. As a floating plant it needs no substrate, and its roots act as a natural nutrient filter that helps starve algae.

Maintenance

Thin the floating mat regularly so light still reaches plants below. Harvest mature plantlets before they crowd the surface, and remove any yellowing or decaying fronds promptly. Periodically lift the mat to check the dangling roots and trim them if they tangle in equipment or shade rooted plants too heavily.

Common Challenges

Surface overgrowth: fast growth quickly blocks light to the tank below, so thin often.
Melting after a move: leaf form changes between submerged and emersed growth, and fronds may shed before new ones adapt.
Tangled roots: long roots can foul filters and heaters if left unchecked.