Species description

Care, breeding and tankmates

Plant profile

Placement

Floating

It floats entirely on the surface, making it perfect for open-topped aquariums or paludariums where it can be viewed from above. It serves as an excellent natural shade provider for anubias, bucephalandra, and other low-light epiphytes. It should be corralled if the entire surface should not be covered.

Botanical form

Floating, Fern

Azolla cristata forms small, compact, and highly branched fronds with tiny, overlapping leaves that resemble microscopic pine branches. The leaves feature fine, water-repellent hairs on their upper surface, keeping the plant buoyant. Its roots are relatively short and feathery compared to other floating plants like Pistia.

Growth

Fast

The growth rate is exceptionally fast, especially in warm, nutrient-rich environments with intense lighting. It can quickly multiply to blanket the entire water surface in a short period. This rapid growth makes it a great ally against algae but requires the aquarist to be diligent with removal.

Substrate

None

This aquatic floating fern thrives purely on the water surface, requiring no substrate whatsoever for anchoring or nutrition. Its fine rootlets are suspended in the water column, efficiently extracting free-floating macronutrients directly from the environment. Because it obtains everything it needs from the water and air, the composition of the aquarium's substrate has no impact on its growth.

Column fertilization

Recommended

Liquid fertilization is the sole method of providing necessary elements (other than nitrogen) to this plant. A complete liquid fertilizer dosed directly into the water column will ensure healthy, dense growth. It readily absorbs whatever is available in the water, often acting as a biological filter.

Root fertilization

None

Because it is a free-floating fern with roots that never touch the substrate, root fertilization is entirely irrelevant. Nutrients in the substrate are inaccessible to Azolla cristata unless they leach into the water column.

Trimming

Occasional

There is no need for scissors; simply scoop out excess growth with a net or by hand. It is vital to thin out the population regularly to prevent it from forming a thick, impenetrable mat that blocks light and oxygen exchange. Always discard excess plants in the trash, never into natural bodies of water.

Propagation

Division, Fragmentation

Propagation occurs continually through vegetative division. The brittle fronds naturally break apart as they grow, and each tiny fragment will develop into a new, full-sized cluster. Sexual reproduction via spores is rare in the home aquarium.

Sensitivity

Moderate

This plant dislikes strong surface agitation and splashing from filter returns, which can submerge and drown the fronds. It prefers high humidity but can be susceptible to rot if water consistently drips onto it from a condensation cover. It handles a wide temperature range but thrives in warmer, tropical setups.

Layout role

Floating

Its primary function is to provide top-cover, reducing light intensity and offering hiding places for surface-dwelling fish and fry. The delicate, textured mat it forms is aesthetically pleasing, particularly when it displays a mix of green and red hues. It adds a natural, swamp-like or jungle feel to the aquascape.