Azolla
Azolla filiculoides
Synonyms Mosquito fern · Azolla caroliniana · Fairy moss
Azolla (Azolla filiculoides) is a floating plant for the surface, growing to about 1 cm (0.4 in) at a fast pace. It wants 59–82°F (15–28°C), medium light and no CO₂, and counts as an easy plant to keep alive.
At a glance
| Type | Floating plant |
|---|---|
| Light | MediumThe least light it survives in, not the light it looks best in. |
| CO₂ | Not neededWhether it survives without added CO₂ — not whether CO₂ would help it grow faster. |
| Difficulty | Easy |
| Temperature | 59–82°F (15–28°C) |
| Max height | 1 cm (0.4 in)Grown submersed, left to mature, never trimmed. |
| Growth rate | Fast |
| Placement | floating |
| pH | 6–8 |
Before it goes in
- Azolla needs medium light. Under a low-light LED it thins out instead of filling in.
- It grows without CO₂.
- It only colours up under strong light with CO₂; in a low-tech tank it stays green.
- It stays around 1 cm (0.4 in), low enough to keep the front glass clear.
- Its leaves are medium: Goldfish, Electric Yellow Lab and Colombian Ramshorn Snail will eat it.
Can it grow without CO₂?
Yes. Azolla does not need CO₂ at all.
How much light does it need?
Medium light — and that is the survival line, not the “it looks better” line. Colour is a separate question: it only turns red under strong light with CO₂.
How big does it get?
About 1 cm (0.4 in) tall when it is mature and untrimmed, growing fast, and it does not root at all.
Will my fish eat it?
Its leaves are medium, so some will: Goldfish, Electric Yellow Lab and Colombian Ramshorn Snail.
What it goes with
- Plants that run on the same light and CO₂, so they can share a tank without one of them being the odd one out: Hygrophila corymbosa 'Siamensis', Anubias nana 'Petite', Cryptocoryne wendtii and Hygrophila corymbosa 'Compact'.
- Animals that share its temperature range and will not eat or uproot it: Betta, Cherry Shrimp, Angelfish and Bristlenose Pleco.
Often compared with
| Azolla | Duckweed | Giant Duckweed | |
|---|---|---|---|
| Light | Medium | Low | Low |
| CO₂ | Not needed | Not needed | Not needed |
| Max height | 1 cm | 0.5 cm | 0.5 cm |
| Difficulty | Easy | Easy | Easy |
More plants
Sources (2) · checked Sep 2026
- Light, CO₂, Difficultyaquaticarts.com
- Colorflowgrow.de