Species description

Care, breeding and tankmates

Plant profile

Placement

Floating

It is a floating plant that resides exclusively on the water's surface. It can be used to dim the lighting for plants below or to provide a dense mat for surface-feeding fish and labyrinth fish to build bubble nests. In open-topped tanks, it provides a striking visual element when viewed from above.

Botanical form

Floating, Fern

Azolla filiculoides is a small floating fern composed of tiny, overlapping, scale-like leaves. The fronds are relatively loose and spreading compared to other Azolla species, giving it a slightly more open appearance. The leaves are water-repellent, and numerous fine roots hang beneath.

Growth

Fast

This species has one of the fastest growth rates of any aquatic plant, capable of doubling its surface coverage in just a few days under ideal conditions. It will aggressively uptake nutrients from the water, making it a superb natural filter. Consequently, frequent and substantial harvesting is mandatory.

Substrate

None

Azolla filiculoides is a free-floating fern that completely eschews substrate anchoring. Its small, dangling roots absorb dissolved nutrients directly from the water column, while it fixes its own nitrogen in symbiosis with cyanobacteria. The tank's bottom composition is entirely irrelevant, though the plant demands nutrient-rich water to multiply rapidly.

Column fertilization

Recommended

Liquid dosing is the only way to fertilize this plant. A well-rounded liquid fertilizer program will ensure it doesn't deplete the water of essential micro and macronutrients. Care must be taken not to overdose, as this plant is very efficient at absorbing whatever is available.

Root fertilization

None

Root tabs and enriched substrates are entirely ineffective for Azolla filiculoides. It is a strictly floating species, meaning its roots rely solely on the water column for nutrient acquisition.

Trimming

Occasional

Routine maintenance consists of physically removing large portions of the plant mass from the aquarium surface. It should not be allowed to form a multi-layered, thick mat, as this can severely restrict gas exchange and light penetration. Discard the removed biomass safely in a compost bin or trash.

Propagation

Division, Fragmentation

Propagation happens effortlessly through vegetative fragmentation. The plant naturally breaks into smaller pieces as it grows, rapidly spreading across the surface. No intervention is required by the aquarist to encourage propagation.

Sensitivity

Moderate

It prefers calm water surfaces; strong currents from filters or powerheads can damage the fronds and push the plant underwater, leading to decay. It is also highly sensitive to condensation dripping from tightly sealed aquarium lids. Ensuring proper ventilation above the water surface will help prevent rot.

Layout role

Floating

As a surface floater, it plays a critical role in light management and providing shelter at the very top of the water column. The delicate roots create a microhabitat for fry and small shrimp. Aesthetically, its potential to turn deep red adds a dramatic flair to the upper reaches of the aquascape.