Subwassertang

Quick facts

Max height

8 cm

Growth rate

slow

Difficulty

beginner

Placement

midground

Propagation

fragmentation

Water parameters

Temperature

18–28°C

pH

5.0 to 7.5

Hardness

0 to 15 dGH

Light and nutrients

Lighting

low

CO2

not required, but boosts growth and color

Substrate

epiphyte

Feeding

feeds from the water column (use liquid fertilizer)

Substrate

What this plant roots into (or attaches to). The substrate affects both plant nutrition and water chemistry; see each linked page for full effects.

This plant feeds primarily from the water column, so substrate choice matters more for its fish-tank compatibility than for plant nutrition.

With fish

Plant-eating fish

safe with plant-eating fish (tough leaves or unpalatable)

Diggers (corydoras, loaches)

fine - root system or attachment style handles it

Root-disturbing fish

tolerates fish that disturb roots

Habitat

The origin and taxonomy of subwassertang are unusual: it's a liverwort (Lomariopsis lineata or a closely related species, identification debated) that grows as flat, irregularly branching, semi-translucent green fronds resembling small pieces of seaweed or lettuce. The name 'subwassertang' is German for 'freshwater seaweed,' coined by German aquarists who first introduced the plant to the hobby. Its exact geographic origin is unclear; it may come from tropical Asia. The growth form is unique among common aquarium plants: no stems, no roots in the traditional sense, just flat, branching thalli that slowly expand. The texture is unlike any other freshwater aquarium plant. The taxonomic identity remains debated; molecular analysis has linked it to the fern genus Lomariopsis, but the aquarium form appears to be a gametophyte (juvenile fern stage) that never develops into the mature sporophyte form. This perpetual gametophyte growth is unusual and may explain why the plant looks nothing like a typical fern. The name 'subwassertang' was coined by the German aquarium hobby community and has been adopted internationally despite not being a formal scientific name.

Care notes

Very easy. Grows in any light (low to high), any temperature (18–28°C), any water chemistry, and without CO2. The plant can be attached to hardscape with mesh or thread, left loose in the tank (it sinks naturally and accumulates on the bottom), or stuffed into crevices in driftwood and rocks. Growth is slow; the flat thalli expand gradually, with new growth branching from the edges. Under moderate light with nutrients, growth accelerates slightly but remains slow. The plant doesn't need trimming in the traditional sense; remove excess portions by hand when the mass becomes too large. Subwassertang provides excellent surface area for biofilm, making it one of the best plants for shrimp tanks alongside Java moss. Baby shrimp hide within the tangled fronds and graze on the biofilm coating. The unique seaweed-like texture adds visual variety in tanks dominated by traditional stem and rosette plants. Propagation by fragmentation: break off a piece and place it somewhere else. Any fragment grows. Available from specialty aquatic plant retailers and hobbyist trades; not commonly stocked at general pet stores.

Further reading

• How to cycle a fish tank
• Water chemistry for fishkeepers: pH, GH, KH, and what they mean