Riccia and the Floating Plant That Aquascapers Decided Should Live Underwater

# Riccia and the Floating Plant That Aquascapers Decided Should Live Underwater I discovered Riccia fluitans the way most people do: I was looking for something completely different and ended up with a bag of what looked like green cotton wool. The seller at the aquatics fair said it was “versatile” and left it at that. I got home, researched it properly, and realised I’d bought a plant that had spent millions of years evolving to float on water surfaces, which the aquascaping community had collectively decided should be tied to rocks and forced to live underwater instead.

Classic human logic, really. Three tanks later, I’ve got Riccia growing in all of them. It turns out that when you force an aquatic liverwort to do something it wasn’t designed for, interesting things happen.

Not always good things, but definitely interesting ones. ## Quick Reference | **Care Level** | **Lighting Needs** | **CO2 Required** | **Growth Rate** | **Max Size** | **Our Rating** | |—|—|—|—|—|—| | Intermediate | High | Yes (recommended) | Very Fast | 1-5cm carpet | 7/10 | ## The Liverwort That Changed Aquascaping Riccia fluitans isn’t technically a plant. It’s a liverwort, which puts it somewhere between moss and proper aquatic plants on the evolutionary timeline.

It’s found naturally across most temperate and tropical regions, floating on the surface of still or slow-moving water bodies.

The species has been around for considerably longer than the hobby that decided to submerge it. The shift happened sometime in the early 2000s when aquascapers started experimenting with forcing surface plants underwater. Takashi Amano popularised the technique of tying Riccia to hardscape with fishing line or cotton thread, creating those impossibly green, bubble-covered carpets that dominated competition tanks for years.

What had been a simple floating plant suddenly became one of the most demanding and visually striking elements in high-tech planted aquariums. The technique worked because Riccia, when submerged and given enough light and CO2, produces oxygen bubbles that get trapped in its fine, branching structure. The visual effect is remarkable: a bright green carpet that looks like it’s constantly fizzing.

It became the signature look of the nature aquarium style, even though keeping it healthy underwater requires fighting against everything the plant evolved to do. Today, you’ll find Riccia in most specialist aquatic plant suppliers, sold specifically for this underwater application. The irony is that it’s often more expensive and harder to keep alive than plants that actually evolved to live submerged. ## What Makes Riccia Special The first thing you notice about healthy submerged Riccia is the pearl.

That’s the term for the oxygen bubbles that form across the surface during periods of active photosynthesis. Under strong lighting with adequate CO2, every tiny branch becomes studded with micro bubbles that rise slowly towards the surface. It’s one of the most obvious visual indicators of healthy plant growth you can get in an aquarium.

The structure itself is unlike any conventional aquatic plant. Riccia grows as a thallus, essentially a flat, branching body without true roots, stems, or leaves. Each piece branches repeatedly, creating a dense, three-dimensional mat.

When tied properly to hardscape, this creates texture that’s impossible to achieve with stem plants or traditional carpeting species. The effect is particularly striking over pale sand or against dark volcanic rock. Growth rate is where Riccia becomes either your best friend or biggest problem, depending on how you look at it.

Under optimal conditions—high lighting, CO2 injection, and adequate nutrients—it can double in size within two weeks (Tropica). This makes it excellent for filling space quickly in a new aquascape, but it also means constant maintenance to prevent it from completely taking over the tank. The plant’s tolerance ranges are broader than many high-tech species, which partly explains its popularity.

It handles temperatures from 10–28°C, though it performs best around 20–28°C (Fishkeeper). pH can range from 5.0–8.0 (Fishkeeper), making it adaptable to both soft and moderately hard water setups. This flexibility means it can work in tanks where more finicky species would struggle. The attachment method is crucial to success.

Cotton thread works well because it biodegrades as the Riccia establishes itself. Fishing line is more permanent but can cut into the plant if tied too tightly. Some aquascapers use hairnets or aquarium-safe mesh, which distributes the weight more evenly and creates a more natural spreading pattern.

The key is securing it firmly enough to prevent floating but loosely enough to allow growth. Lighting requirements are non-negotiable. Riccia needs high light intensity to photosynthesize effectively underwater (Aquarium Industries PDF).

Insufficient lighting results in leggy, pale growth that eventually detaches and floats to the surface, returning to its natural habitat preference. CO2 injection, while not technically essential, makes the difference between surviving and thriving (Tropica). ## The Honest Assessment The biggest challenge with submerged Riccia is that you’re working against evolution. This plant wants to float, and it will try to return to the surface at every opportunity.

Inadequate attachment methods result in chunks breaking free and forming floating mats that block light from plants below. I’ve spent more time than I care to admit fishing escaped Riccia out of filter intakes. Maintenance is relentless.

The growth rate that makes Riccia impressive also makes it labour intensive. Left unchecked for more than three weeks, it can smother other plants and disrupt carefully planned aquascapes. Trimming requires complete removal and reattachment, not just cutting back like conventional stem plants.

This means partially dismantling hardscape elements every month or so. The plant’s sensitivity to changes in lighting or CO2 levels can be frustrating. A slight reduction in either causes rapid deterioration, with browning sections that need immediate removal to prevent decay.

Unlike many aquatic plants that adapt gradually to changing conditions, Riccia tends to respond dramatically and quickly. Water quality impacts are significant in high-density plantings. The rapid growth consumes nutrients aggressively, which can lead to deficiencies in other species.

Conversely, if nutrient levels drop too low, dying Riccia can release organic compounds that trigger algae blooms. The balance requires constant attention. Cost adds up over time.

While individual portions aren’t expensive, the need for regular replacement due to maintenance trimming means ongoing expense. Many aquascapers end up dedicating a separate propagation tank just to maintain their Riccia supply. Finally, it’s not suitable for all aquascaping styles.

The intense green colour and fine texture can overwhelm subtle designs. It works brilliantly in high-energy nature aquarium styles but can look out of place in Dutch or Iwagumi layouts that depend on restraint and negative space. ## Legacy and Influence Riccia’s transformation from floating plant to aquascaping staple represents one of the more creative adaptations in the hobby’s history. The technique pioneered with this species opened up possibilities for using other non-aquatic or semi-aquatic plants in submerged applications, expanding the palette available to aquascapers significantly.

The visual language it established—that pearling, bubble-covered carpet effect—became synonymous with high-tech planted tank success. For years, a pearling Riccia carpet was the benchmark image used to demonstrate healthy plant growth and proper CO2 management. Competition aquascapes throughout the 2000s featured it prominently, and it influenced how judges evaluated plant health and aquascaping technique.

Its maintenance requirements also pushed aquascaping towards more intensive management practices. The monthly complete reconstruction needed to maintain Riccia properly normalised the idea that serious planted tanks required regular, disruptive maintenance. This shifted expectations around what level of effort aquascaping demanded and influenced the development of more accessible, lower-maintenance alternatives.

The species remains relevant in contemporary aquascaping, though it’s no longer the automatic choice it once was.

Modern techniques have developed more sustainable approaches to carpeting, but Riccia’s unique aesthetic keeps it in rotation for aquascapers who want that specific bubble-covered, high-energy look. ## The Verdict Riccia fluitans underwater is a triumph of forcing function over form, and it mostly works. If you want that classic high-tech planted tank aesthetic with vigorous pearl and an intensely green carpet that photographs beautifully, this delivers it better than any alternative I’ve tried.

The maintenance burden is real, though. This isn’t a plant you add and forget about. It needs monthly attention, high-end lighting, CO2 injection, and regular replanting.

It’s aquascaping on hard mode, which can be satisfying if you enjoy the process but exhausting if you just want a nice-looking tank. I’d recommend it for intermediate to advanced aquascapers who are already running high-tech setups and want to push their skills further. If you’re working with medium light and no CO2, skip it entirely.

If you’re new to planted tanks, get comfortable with easier species first. But if you’ve got the setup and the commitment, few plants create as dramatic an impact as properly maintained underwater Riccia. See where this placed in our full ranking of aquarium plants.