Azolla Caroliniana

Quick facts

Identity

Also known as

Mosquito fern; Fairy moss; Carolina mosquito fern; Water fern

Synonyms

Azolla cristata

Environment

Freshwater

Native to

United States, Central America, South America

Habitat

Still or slow-moving fresh water such as ponds, ditches, sluggish streams, and swamps

Sourcing

Aquacultured

Conservation

Not Evaluated

Care

Care level

Easy

Growth form

Floating

Max height

0.4 in (1 cm)

Spread

0.8 in (2 cm)

Growth rate

Fast

Placement

Floating

Water

Temperature

60 – 82 °F (16 – 28 °C)

pH

6.0 – 7.5

GH

0 – 15 dGH

Flow

Low

Light

Medium

CO₂

Not needed

Planting

Substrate

Not needed

Feeds from

Water column

Fertilizer needs

Medium

Colors

Green, Red, Orange, Brown

Feeding & breeding

Propagation

Runners

Something wrong or missing? Submit a correction

Care guide

Overview

Suited to low-flow community and shrimp tanks looking for surface cover, this floater forms a dense micro-textured mat of fronds under half an inch across. Colour shifts from gray-green to orange and red under stronger light, staying plain green when dim. Fast-growing and undemanding, it needs regular thinning and still water to avoid sinking and rot.

Care

A tiny free-floating fern that forms a dense, textured mat across the water's surface, with individual fronds barely reaching half an inch across. Under bright light the pinnate fronds shift from gray-green to shades of orange and red, while lower light keeps them a plain green. It tolerates a wide range of temperatures and water chemistry, making it one of the more forgiving floaters for both tropical tanks and cooler setups, but it needs still or very gently moving water since strong surface agitation from filter output will push it under and cause it to rot.

Planting & trimming

Simply scatter portions across the water's surface; it is never planted in substrate and needs a calm or very slow-flow area to stay in place. Because it multiplies so quickly, regular thinning with a net is necessary to keep enough open water surface for gas exchange and to prevent shading of submerged plants. It can also be grown emersed in damp, humid conditions outside the main display.

Fertilizing

Roots dangle freely in the water column and absorb nutrients directly, so no substrate feeding is involved. Good growth and reddening depend on adequate phosphorus, potassium, and iron in the water column; a lack of phosphorus can stall growth almost immediately. Liquid fertilization suited to floating plants works better here than root tabs, and the fern's rapid nutrient uptake makes it a useful tool for pulling excess nitrate and phosphate out of a tank.

Propagation

Propagation is almost entirely vegetative: lateral branches break away from the parent mat and form new independent colonies. A small portion moved to a new container with suitable light and nutrients will quickly establish and spread on its own. Sexual reproduction via spores occurs in nature but is rarely relevant in aquarium culture.

Problems

Left unchecked it multiplies quickly and can blanket the entire surface, cutting off light to plants below and, in stagnant water, contributing to nighttime oxygen depletion. Fronds trapped under filter outflow or strong current tend to sink and rot rather than recovering. Aside from overgrowth and current sensitivity, it has few disease issues and is not usually eaten by fish.

Sources

1. Azolla, Mosquito fern (Azolla Caroliniana) Care Guide
2. Azolla caroliniana Care Guide: Floating Plant for Aquariums and Ponds
3. Carolina Mosquito Fern (Azolla caroliniana) Care Guide & Plant Profile | Guidarium
4. Fairy Moss - Azolla caroliniana | North Carolina Extension Gardener Plant Toolbox

More Floating plants

Hydrocleys Nymphoides Water PoppyPhyllanthus Fluitans Red Root FloaterPistia Stratiotes/ Water LettuceSalvinia CucullataSalvinia Natans/ Floating Fern