Salvinia natans

Also known as Floating fern, Floating watermoss, Floating moss

FreshwaterFloatingSide shootsPlantlets

Invasive. Salvinia species are regulated as noxious weeds in some areas. Never release into the wild; dispose of in the trash.

Salvinia natans (Salvinia natans) — Le.Loup.Gris · CC BY-SA 3.0

Care at a glance

Light: Medium light
CO2: No CO₂ needed
Growth rate: Fast
Placement: Floating
Type: Floating
Temperature: 64–82°F (18–28°C)
pH: 6.0–8.0
Hardness: 2–15 dGH
Max height: 1.2 in (3 cm)
Spread: 3.9 in (10 cm)
Nutrient uptake: Water column
Growth region: Submersed or emersed
Difficulty: Beginner
Origin: Central/Eastern Europe and Asia
Family: Salviniaceae

Overview

Float it on the surface and it grows fast under medium light with no CO2 or substrate, pulling nutrients straight from the water column to help starve out algae and shade the tank. It branches and divides on its own, so you keep it going simply by removing excess, and it stays low and small unlike taller floaters. The main pitfalls are heavy surface agitation and overhead condensation, which both rot the floating leaves, and very low light, which makes it pale and stringy, so give it calm water and a bright source overhead.

In the wild

Salvinia natans is a free-floating fern native to standing and slow fresh water across central and eastern Europe and much of temperate to subtropical Asia. It grows in ponds, ditches, lakes and quiet river edges with still water, plenty of sunlight and humid air. Unlike most aquarium floaters it is an annual that dies back in cold weather and overwinters as spores in its native range.

Good to know

It is a true floating fern in the family Salviniaceae and is rootless. What looks like a pair of leaves and a hanging root is actually three leaves per node, two oval floating leaves that sit on the surface and a third finely divided submerged leaf that dangles down and does the job of a root. The floating leaves are covered in tiny water-repellent hairs that trap a film of air and keep the plant from getting waterlogged.

Did you know

Those hairs on the floating leaves are some of the most water-repellent structures known in nature, with whisk-shaped tips that hold a permanent layer of air, an effect studied by engineers for drag-reducing and self-cleaning surfaces.