Azolla (Azolla filiculoides) care guide

Group
Plants
Other names
Water fern, Moss fern, Fairy moss, Azolla caroliniana (misapplied)
Family
Salviniaceae (floating fern family)
Origin
Warm temperate and tropical Americas
Water
freshwater
Maximum size
2 cm
Temperature
5–28°C
pH
6–8
Hardness
Tolerant (estimate)
Care level
beginner
Lighting
Medium to high light; CO2 not needed
Flow
Still water; dislikes surface flow

Care

Legal note: this plant may not be sold on Aquatic-Auctions to buyers in England and Wales, where its sale is banned (check GOV.UK for the current rules). Azolla filiculoides, the water fern, is a tiny floating fern from warm temperate and tropical America, introduced across Europe, Africa, Asia, New Zealand and elsewhere. Each plant is 1–2 cm across, green with pink, orange or red edges, and covered in water-repellent hairs. It was long misnamed Azolla caroliniana. Like other Azolla it carries nitrogen-fixing cyanobacteria (Anabaena azollae) in its leaves. It grows very fast, branching and breaking into pieces, and can cover a lake within months, especially in nutrient-rich water. Its mats block light and cause low oxygen as debris rots, harming water quality and wildlife. It has been spread with aquarium and pond plants, fish fry and ballast water. It does not tolerate cold well, dying back in winter and surviving as submerged buds. Never release this plant or dispose of it in drains or waterways; it is invasive in some countries. Water figures are our estimate, not from the sources. Sources: Wikipedia (en.wikipedia.org/wiki/Azollafiliculoides); Wikipedia, List of freshwater aquarium plant species. Checked October 2026.

Breeding

Spreads by fragmentation as plants break apart. Do not propagate for sale in England and Wales; dispose of surplus in household waste, never in waterways.

Compatibility and tank mates

Goldfish and many larger fish eat it. Covers the surface quickly, cutting light to plants below and gas exchange for fish, so remove a share every week. Floating plants dislike strong surface flow.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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