Salvinia
Salvinia minima
Also known asCommon salvinia · Water spangles · Floating fern
Water parameters
Light and nutrients
Substrate type: epiphyte. Propagation: fragmentation.
Substrate compatibility
| Substrate | pH effect | Nutrient load |
|---|---|---|
| Wood and rock mounts (Hardscape mount) | varies | none |
| Inert sand (Pool filter sand) | neutral / inert | none |
| Inert gravel (Aquarium gravel) | neutral / inert | none |
| Bare bottom (no substrate) (Bare bottom) | n/a | none |
| Aquasoil (ADA Amazonia) | lowers pH | very high |
| Mineralized clay substrate (Seachem Fluorite) | neutral / inert | moderate |
With fish
Origin and habitat
A small free-floating fern of the family Salviniaceae, Salvinia minima, called common salvinia or water spangles, native to South America, Mesoamerica and the West Indies. It floats in pairs of small oval bright-green leaves, 5–15 mm across, whose upper surface is covered in fine water-repellent hairs that trap air and give a velvety look; the third leaf of each whorl is modified into a feathery, root-like structure that hangs in the water, since the plant is rootless. It spreads by fragmentation and budding into surface mats. Introduced to the United States in the 1920s-30s, first recorded on Florida's St. Johns River in 1928, it is now an international invasive that can blanket still water, shading out submerged plants and crashing oxygen. The much larger S. molesta, giant salvinia, is a distinct species and one of the world's worst aquatic weeds; S. minima is the manageable aquarium one, but no Salvinia should ever be released into the wild.
Outdoor pond use
- USDA zones
- 8–13 (winter low around -12°C or warmer)
Care notes
An easy floating plant. It grows under low to high light in almost any water chemistry across a wide temperature range, with its one real dislike being surface turbulence, so it needs calm water and a baffled filter return. Growth is fast, often doubling its cover in a week or two, so thin it regularly to stop it sealing the surface. The hanging leaf-roots and dense mat shelter fry and shrimp and give grazing biofilm, and the plant pulls nitrate and phosphate from the water, which is why salvinias are used in wastewater treatment and why it earns a place in nutrient-stripping aquaponics, though it is slower at it than duckweed. Leave a gap in the lid so condensation does not drip onto and rot the leaves. It propagates itself by fragmentation and daughter plants. It is genuinely useful in aquaponics as a floating nutrient filter, but because it is so invasive, never release it or dump tank water outdoors.