How do you care for water sprite? Water sprite (Ceratopteris thalictroides) is a fast aquatic fern you can plant in substrate or float at the surface. Give it medium light, warm water above 60°F (16°C), and regular nutrients. Tropica rates its CO2 need as low, though extra CO2 can speed growth. Trim often and replant the baby plantlets.
Key takeaway: Water sprite is a fast, forgiving aquarium fern that soaks up nutrients and helps limit algae. Grow it rooted or floating in medium light and warm water, trim it often, and pot up the plantlets that form on its leaves. Never release it outdoors; UF/IFAS calls it a pantropical aquatic weed.
| Need | Water sprite range | Source |
|---|---|---|
| Light | Medium | Tropica |
| CO2 | Low; extra CO2 may speed growth | Tropica |
| Size | 6–12+ in (15–30+ cm) tall, 4–8 in (10–20 cm) wide | Tropica |
| Temperature | Cannot survive below 60°F (16°C) | UF/IFAS |
| Placement | Rooted or floating | Ferns of Texas, Tropica |
| Propagation | Plantlets on leaf margins | Ferns of Texas |
What Is Water Sprite?
Water sprite is Ceratopteris thalictroides, a short-lived aquatic or semi-aquatic fern. The Ferns of Texas flora describes it as usually rooting but sometimes floating, with two leaf types and small plantlets in notches along the leaf margins. UF/IFAS lists it as native to Asia, with its exact native range unclear.
Tropica describes it as a pantropical fern 6–12 inches (15–30 cm) tall and 4–8 inches (10–20 cm) wide. Its finely branched leaves contrast well with broad-leaved plants like anubias and java fern.
Should Water Sprite Be Planted or Floated?
This fern can be planted or floated, and both work. Rooted plants form upright rosettes in the substrate, while floating plants spread across the surface and shade the tank below. Ferns of Texas notes the species is usually rooted in mud but sometimes floats, so pick the form that suits your tank layout.
- Planted: bury only the roots and keep the crown above the gravel.
- Floating: drop it on the surface and keep it away from strong filter outflow.
- Open tanks: Tropica says it can grow out of small open aquariums and form surface leaves.
Floating mats give fry and small fish cover, a benefit also seen with duckweed.
What Light and CO2 Does Water Sprite Need?
Water sprite needs medium light and has a low CO2 demand, according to Tropica. Tropica says the plant normally grows fast, but adding CO2 may be necessary to boost growth. In good light it consumes large amounts of nutrients, which Tropica says helps prevent algae and makes it a good starter plant for small aquariums.
- Provide medium light; a basic planted-tank LED is usually enough.
- Run the light on a steady daily timer.
- Dose a liquid fertilizer if leaves pale.
- Add CO2 only if growth stalls in bright light.
For light choices, see our guide to a grow light for aquarium plants.
What Water Temperature Suits Water Sprite?
Keep this fern in warm, tropical water. UF/IFAS says its range is limited by climate because it cannot survive below 60°F (16°C), and it needs high-nutrient, slow or still water. That makes it a good fit for heated tropical tanks but a poor choice for cold-water setups or unheated winter ponds.
Ferns of Texas notes that the species persists in constant-temperature springs in Texas, which shows how much it depends on steady warmth.
How Do You Propagate Water Sprite?
The fern propagates from plantlets that grow on its leaves. Ferns of Texas describes adventitious buds or small plantlets in notches along the leaf margins. When a plantlet has a few leaves and roots, pull it gently from the parent leaf and float it or plant it in the substrate.
- Wait until the plantlet has small roots of its own.
- Pinch or snip it off the parent leaf.
- Float it, or press its roots lightly into the substrate.
- Remove old, yellowing leaves from the parent.
The plant also reproduces by spores from the fertile, finely divided leaves, which is one more reason to keep it inside.
Is Water Sprite Invasive?
Water sprite can become a weed outside the aquarium. UF/IFAS calls Ceratopteris thalictroides a pantropical aquatic weed spread by the aquarium and fishpond trade, reported in South Florida as early as 1878. It spreads easily by spores and plant fragments, so never dump trimmings or tank water into ditches, ponds or streams.
- Bag and trash trimmings instead of composting them near water.
- Do not use it in outdoor ponds in warm regions.
- Check local rules before buying.
Why Is My Water Sprite Melting or Pale?
A pale or melting water sprite usually points to low nutrients, low light or cold water. Because it is a heavy feeder, it can use up nutrients quickly in a planted tank. Check that water stays above 60°F (16°C), add a balanced liquid fertilizer, and remove decaying leaves so they do not foul the water.
For dosing basics, see fertilizer for plants in water.
Can water sprite float?
Yes. It can grow rooted or floating. Floating plants spread over the surface and shade the tank, while rooted plants form upright rosettes.
Does water sprite need CO2?
Not usually. Tropica rates its CO2 demand as low, though it notes added CO2 may be needed to promote faster growth.
How fast does water sprite grow?
Tropica describes it as fast-growing in good light, reaching about 6–12 inches (15–30 cm) or more within about two months in the tank.
Is water sprite good for beginners?
Yes. Tropica calls it a good starter plant for small aquariums because it grows fast and consumes nutrients that algae would use.
Can goldfish live with water sprite?
They can share a tank, but water sprite cannot survive below 60°F (16°C), per UF/IFAS, so it suits only heated goldfish tanks.
Sources
- Tropica Aquarium Plants. Ceratopteris thalictroides/4405).
- University of Florida IFAS Center for Aquatic and Invasive Plants. Ceratopteris thalictroides.
- Botanical Research Institute of Texas. Ferns of Texas: Ceratopteris thalictroides.
- Photo credits (Wikimedia Commons, edited with titles): Ceratopteris thalictroides by Show_ryu (CC BY-SA 3.0); Ceratopteris cornuta kz02 by Krzysztof Ziarnek, Kenraiz (CC BY-SA 4.0); Planted Tank 03 – Flickr – The Wandering Angel by The Wandering Angel from Makati City, Philippines (CC BY 2.0)