Propagating Fontinalis antipyretica (Willow Moss) by Division

A guide to propagating Willow Moss by division: split the clump, tie pieces to wood or rock, and keep this robust coldwater moss thriving in cool, oxygen-rich water.

Overview

Fontinalis antipyretica, the greater water or willow moss, is a robust aquatic moss found in both still and flowing freshwater across Europe, Asia, Greenland and Africa. It grows attached to submerged rocks in fast-flowing streams, across lake beds, and as floating masses in still water, forming large clumps and mats. Its branched, trailing stems reach up to 60 cm and are triangular in cross-section, bearing stiff, keeled, lance- to egg-shaped leaves 4–9 mm long arranged in three overlapping rows.

It is a cool-water species traditionally kept in unheated aquaria, favouring shaded positions and oxygen-rich water. It is one of the larger and slower mosses, so it does not scale down well into small tanks.

Propagation Method (Division)

Willow moss reproduces primarily through stolons and the rooting of detached fragments, so it is propagated by division rather than spores. Splitting the clump into smaller pieces and securing them to hardscape lets each portion attach and grow on independently. Sexual reproduction via spores occurs in spring but is uncommon and unnecessary for the aquarium.

Step-by-Step

Lift a healthy clump and rinse away trapped debris in cool, tank-temperature water.
Split it by hand into smaller portions, each with several trailing stems.
Lay each portion against the wood or rock you want to cover.
Tie it on with cotton thread or fishing line, or fix a small tuft with a drop of gel superglue held for about 15 seconds.
Place it where current is steady and light is modest, and leave it to anchor and beard downward.

Conditions for Healthy Growth

Temperature: a coldwater species — keep it cool (roughly 10–22°C) and avoid warm tanks.
Flow: strong, steady current best mimics its native streams and keeps it oxygenated.
Light: low to modest, with shaded positions favoured.
Oxygen: needs an oxygen-rich environment; good surface movement helps.
Water: soft to hard, slightly acidic to slightly alkaline; CO2 is not required.

Maintenance

Willow moss looks best trimmed short; left to grow out it becomes leggy and less bushy. Trim regularly and re-attach the cut pieces as fresh divisions. During water changes, brush detritus off the fronds and keep flow strong so the clump stays clean and dark green.

Common Challenges

Because it grows slowly and large, it suits bigger or coldwater setups better than small warm aquaria. Stagnant water and poor oxygenation lead to browning and detritus build-up.