Propagating Subwassertang: Splitting the Clump

Subwassertang is a rootless fern gametophyte that multiplies by fragmentation. Learn to break the clump into pieces and tie it onto hardscape, since it won't anchor firmly itself.

Overview

Subwassertang (Lomariopsis lineata, also called round pellia or Loma fern) is not a true plant in the everyday sense but a freshwater fern gametophyte (prothallium). It forms flat, branched, bright-green thalloid lobes that are only one cell-layer thick and have a moss- or liverwort-like appearance. It has no true roots, stems or leaves, so it cannot anchor itself the way rooted plants do.

First found in the aquarium of botanist Christel Kasselmann in 2001, the aquarium specimens are believed to be clones of that single original. It is native to Southeast Asia, grows slowly under low to moderate light, and is a favourite in shrimp tanks for the biofilm and shelter it provides.

Propagation Method (Division)

In cultivation Subwassertang reproduces entirely by fragmentation: pieces that break off simply grow into new clumps. To propagate it you break or divide the clump into smaller pieces, then attach each piece to hardscape. Because the gametophyte has no roots, it will not grip a surface firmly on its own, so it must be tied or held in place.

Step-by-Step

Lift the parent clump and gently pull or cut it into several smaller pieces.
Choose your mounting surface, such as driftwood, rock, or a piece of plastic mesh.
Lay each fragment flat against the surface in a thin layer.
Secure the pieces with cotton thread, fishing line, or by sandwiching them in mesh, since they will not attach firmly by themselves.
Place the mount in an area with gentle flow so detritus does not smother the lobes.
Leave it undisturbed; the pieces continue to spread and branch over the surface.

Conditions for Healthy Growth

Subwassertang is undemanding and tolerant of a wide range of conditions. It does not need CO2 or strong light and is happy in tanks with minimal flow, such as those running a sponge filter. Growth is slow, so patience is needed while a new clump establishes.

Temperature: 18-28 C
pH: 6.0-7.5
GH: 2-15
Light: low to moderate; no CO2 required
Flow: tolerates minimal flow, ideal for shrimp tanks

Maintenance

Trim the clump roughly every three weeks to keep it tidy; the trimmings are themselves new propagules and can be tied down elsewhere. Occasionally lift and shake the clump or run a gentle siphon over it to dislodge trapped debris, which keeps the interior bright green.