Subwassertang

Quick facts

Identity

Also known as

Süsswassertang; Round Pellia; Pellia Moss; Loma Fern

Synonyms

Pteris sp.; Lomariopsis sp.; Lomariopsis cf. lineata

Environment

Freshwater

Native to

Southeast Asia (exact origin of aquarium clone unknown)

Habitat

Freshwater aquaria; wild fern grows epiphytically on trees or among rocks in humid forests and riverbeds, but the aquarium form is a perpetual submerged gametophyte

Sourcing

Captive-bred

Conservation

Not Evaluated

Care

Care level

Easy

Growth form

Moss

Max height

4 in (10 cm)

Spread

12 in (30 cm)

Growth rate

Slow

Placement

Foreground, Midground, Background, Floating, Epiphyte

Water

Temperature

68 – 82 °F (20 – 28 °C)

pH

6.0 – 7.5

GH

0 – 15 dGH

Flow

Low

Light

Low

CO₂

Not needed

Planting

Substrate

Not needed

Feeds from

Water column

Fertilizer needs

Low

Colors

Green

Feeding & breeding

Propagation

Rhizome division

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Care guide

Overview

Subwassertang is a rootless fern gametophyte forming a dense mat of translucent, ribbon-like green fronds rather than true leaves. It spreads slowly by fragmentation alone, tolerating low light and no CO2, though calm flow is needed to keep the fragile thallus from tearing apart. Widely used as shrimp grazing cover or fry refuge in nano tanks.

Care

This plant is essentially foolproof, tolerating low light, no CO2, and a wide range of temperatures and water chemistry. It has no true roots or stems, growing instead as a translucent, ribbon-like thallus that slowly expands into a dense mat over hardscape or substrate. Because it lacks rigid structure, strong flow can tear it apart and scatter fragments throughout the tank, so placing it in calmer areas helps keep growth contained. It can be left loose, wedged into crevices, or tied to wood and rock, where it will eventually anchor itself as it grows.

Planting & trimming

No substrate is needed since the plant has no root system; it can be tied or glued to driftwood and rock with thread, fishing line, or cyanoacrylate gel glue, left to float freely, or simply allowed to rest loosely on the substrate where it will spread as a mat. It is commonly used as a carpet-like accent, a background clump, or stuffed into breeder boxes and shrimp tanks as cover. Trimming is done simply by pinching off overgrown sections, which can be reused elsewhere in the tank.

Fertilizing

Growth is fueled almost entirely by nutrients absorbed directly from the water column rather than through roots or substrate. No fertilizer or CO2 injection is required, though liquid ferts and CO2 will visibly speed up growth and deepen the green color. In nutrient-poor water the fronds can appear pale or thin, which usually resolves once fish waste or light dosing of a liquid fertilizer is introduced.

Propagation

Propagation is entirely by fragmentation; any piece torn or cut from the main mass will continue absorbing nutrients from the water and grow into an independent clump. No special technique is required beyond separating a portion and placing it wherever new growth is wanted. Because of how easily it breaks apart, stray fragments frequently lodge in filters or other decorations and start new colonies unintentionally.

Problems

Excess light intensity can stress the thallus and cause portions to melt or brown, so moderate rather than intense lighting is usually safer. Because the tissue is delicate, rough handling during maintenance or shipping easily shreds it into fragments, though these fragments simply grow into new plants rather than dying off. Algae can become a nuisance once the mat thickens, since the dense, low-flow structure traps detritus and film algae within its fronds.

Sources

1. Süsswassertang - Wikipedia
2. Subwassertang Care Sheet: The Complete Guide - Build Your Aquarium
3. Subwassertang (Lomariopsis lineata) - Scale & Stem
4. Subwassertang: The Ultimate Care & Propagation Guide

More Mosses

Christmas MossFissidens FontanusFlame MossJava MossMini Christmas MossPeacock Moss