Water sprite
Ceratopteris thalictroides
Also known asIndian fern · Water fern · Floating fern
Water parameters
Light and nutrients
Substrate type: any. Propagation: daughter plants.
Substrate compatibility
| Substrate | pH effect | Nutrient load |
|---|---|---|
| Bare bottom (no substrate) (Bare bottom) | n/a | none |
| Inert sand (Pool filter sand) | neutral / inert | none |
| Inert gravel (Aquarium gravel) | neutral / inert | none |
| Aquasoil (ADA Amazonia) | lowers pH | very high |
| Mineralized clay substrate (Seachem Fluorite) | neutral / inert | moderate |
| Dirted tank (mineralized topsoil) (DIY soil substrate) | slightly acidic | very high |
With fish
Origin and habitat
Ceratopteris thalictroides is a true aquatic fern in the family Pteridaceae, native across the tropics and subtropics of Asia, Africa, the Americas and Oceania, reaching as far north as Korea and as far south as western Australia. Its fronds are finely divided and pale green, with a lacy, open texture, and the plant grows rooted in mud or drifting at the surface. The epithet thalictroides points to the resemblance between those divided fronds and the foliage of meadow rue (Thalictrum). It is one of the few aquarium ferns that behaves as a genuine amphibian, doing well submerged, emergent, or floating. Aquarists prize it as a heavy feeder that strips nitrate and phosphate quickly, which is why it turns up so often in newly cycled or overstocked tanks. Several close relatives are sold under similar names: broadleaf water sprite (C. cornuta), the floating antler fern (C. pteridoides), and the laboratory model fern C. richardii are distinct species, not growth phases of one plant.
Care notes
Forgiving for beginners. It survives in low light but pushes its fastest, bushiest growth under brighter conditions, and it does not need added CO2. Water chemistry can range from soft and slightly acidic to moderately hard and neutral, with a working temperature near 20–30°C. Plant it in substrate, where it anchors and grows upright, or leave it floating, where it tends to grow larger and faster with fronds spreading over the surface. Propagation is effortless: small plantlets form along the margins and faces of older fronds, then drop off and root on their own, and the fern also reproduces by spores. Because it can double its mass within a week or two when conditions suit it, trimming and thinning are routine. The dense, feathery growth shelters fry and egg-scatterers, and floating clumps make a handy anchor for bubble-nesting bettas. It stays cheap and is passed around constantly in hobbyist trades.