Azolla Filiculoides (Azolla filiculoides) Care Guide
A tiny floating fern with overlapping scale-like leaves that form dense mats on the water surface. Can turn from green to reddish-brown under strong light, and is one of the fastest-reproducing aquati…
Compiled by Aquairi from published sources · Published · Updated
Overview
Azolla filiculoides is an aquatic plant in the family Salviniaceae. A tiny floating fern with overlapping scale-like leaves that form dense mats on the water surface. Can turn from green to reddish-brown under strong light, and is one of the fastest-reproducing aquatic plants known.
Taxonomy
- Family: Salviniaceae
- Genus: Azolla
- Scientific name: Azolla filiculoides
- Other names: Fairy Moss, Water Fern
Habitat
A floating fern native to warm temperate and tropical regions of the Americas, introduced widely across Eurasia, Africa and Oceania. Hosts the symbiotic cyanobacterium Anabaena azollae in specialised leaf cavities, enabling nitrogen fixation from the atmosphere.
Growth requirements
- Light: low (≈30-50 PAR at substrate)
- CO2: optional (CO2 improves growth and coloration)
- Temperature: 15-28 °C
- pH: 5.5-8
- GH: 2-15 °dGH
- Nutrient demand: low
- Growth rate: fast
- Difficulty: beginner
Placement
- Recommended placement: floating at the surface
- Maximum height: 2 cm
- Trim every: 5 days
Propagation
In cultivation the plant is propagated by vegetative division or fragmentation.
Propagating Azolla filiculoides (Water Fern)
Overview
Azolla filiculoides is a tiny floating fern, each plant only 1 to 2 cm across, green and tinged pink, orange or red at the edges. It harbours the diazotrophic cyanobacterium Anabaena azollae, which fixes nitrogen from the air and contributes to the fern's metabolism. This partnership helps fuel its remarkable speed of reproduction.
Propagation Method
Propagation is by fragmentation. The plant branches freely and breaks into smaller sections as it grows, so each separated piece becomes an independent new plant. You do not cut or plant anything; you simply divide an existing floating mat into portions.
Step-by-Step
- Scoop a healthy section of the floating mat from the surface.
- Break or gently pull it into several smaller clumps.
- Place each clump on the water surface of the target tank.
- Leave them floating; they branch and break apart on their own.
- Within days the portions spread into new mats.
Conditions for Healthy Growth
The fern floats at the surface and prefers calm water and good light. Under strong light it shifts from green toward reddish tones. It is capable of spreading over the surfaces of lakes to give complete coverage in only a few months, so growth is rarely a problem to encourage.
Maintenance
Because it doubles so quickly, the real work is removal, not encouragement. Skim off excess regularly to keep light reaching plants and livestock below. In cooler climates it largely dies back in winter, surviving by means of submerged buds.
Common Challenges
Dense mats block light penetration and can create an anaerobic environment, reducing water quality and aquatic biodiversity. Keeping it thinned is the main ongoing challenge in any tank.