Riccia fluitans or floating Crystalwort is a member species of the liverwort genus Riccia which is famous for its use in aquascaping Nature and Iwagumi aquaria. This plant packs moss-like characteristics, thus it can serve as an alternative to the popular and versatile aquarium plant “Java moss”.
Riccia fluitans is a bright green floating plant that is commonly used to decorate the foregrounds of planted tanks, shrimp, and breeding tanks. It has a fast-growth potential, capable of putting out vivid green tufts in different sections of an aquarium. The species is suitable for all experience levels, hence amateur hobbyists won’t find it difficult growing Riccia fluitans in their tanks.
Keep reading for more information on this amazing Liverwort species, this guide covers how to plant, propagate and care for Riccia fluitans in freshwater aquaria.
| Important: It is illegal to sell (but not to have) Riccia in some states due to its potential to become invasive. So, check your state laws before purchasing. |
Quick Notes about Crystalwort
| Common Name | Crystalwort |
| Other Names | Floating moss, Floating Liverwort |
| Scientific Name | Riccia fluitans |
| Tank Size (minimum) | 10 gallons (~40 liters) |
| Difficulty | Easy to medium |
| Lighting | Moderate to high lighting |
| Optimal pH | 6.0 – 8.0 |
| Water hardness | Soft to moderately hard water (1 – 10). |
| Temperature | 20 – 26 °C (68 – 79 °F) |
| Substrate | Not needed |
| Growth Rate | Fast |
| Placement in Tank | Foreground / midground / floating |
| Fertilizer |
Recommended |
| CO2 | Not needed – for emersed (floater) Recommended – for submersed |
| Propagation | Through spore production |
Interesting fact: The plant is blessed with many medicinal properties including pharmacological, phytochemical content, and biological activities.
Origin of Crystalwort
Riccia fluitans belongs to Ricciaceae, a family of minute liverwort with a flat thallus. The thallus is the undifferentiated body of these plants.
This species was first described by Carl Linnaeus in 1753, in relation to the usage history, Japanese aquascaper Takashi Amano was the earliest user. He incorporated this floating plant in his nature aquarium and had it grown submersed. Due to his exploits, many aquarists have been imbued to aquascape their tanks with this liverwort.
The specific epithet “fluitans” is of Latin origin and it means “floating”, hence the common name — floating Crystalwort.
Habitat of Crystalwort
This species has a cosmopolitan distribution, presently widespread in the Americas, Africa, and Eurasia.
Floating Crystalwort is an amphibious liverwort. The plant has adapted to dwell on moist soil, as well as to life in the water — where they float on the surface or stay submersed, attached to other plants or the bottom.
In the submersed state, Floating Crystalwort prefers shallow or quiet waters — ponds, swamps, ditches, and slow-moving streams.
Description of Crystalwort
Riccia plants forms thick clusters of bright green threads and grows in sphere-shaped clump with slightly flattened.
Floating Crystalwort is a perennial plant that comprises a thallus i.e. a body that is not differentiated into leaves and stems. The plant is capable of branching out profusely, forming numerous shoots— bright green flat growths that are forked, hence giving them a Y-shape.
Moving on to the size, the length of each thallus is often about 0.5 – 2 cm (1/5 – 3/4 inches) long and up to 1 mm (1/25 inches) wide. The body consists of air pores that help the plant remain buoyant in water, other specialized cells are present and these hold chlorophyll and starch for energy production.
If grown emersed, the plant forms root-like structures called rhizoids that anchor the thallus to the substrate. Additionally, the branching thallii of the terrestrial form is two times broader than that of the aquatic form. In this state, emersed Riccia fluitans produces spore capsules whereas aquatic forms tend to reproduce asexually.
Tank Requirements and Water Parameters
Tank size:
The recommended tank size for planting Riccia fluitans is a minimum of 10 gallons (~40 Liters).
Although the plant can also be used sparingly in tanks with lesser capacity (nano tanks) to adorn the foregrounds, I would not recommend doing it as it can quickly overtake system.
Water type, Temperature, Hardness, and pH:
Temperature: Optimal temperature for this plant is between the range 20 – 26 °C (68 – 79 °F). Regardless, the species can survive in waters with temperatures 59 – 86 °F (15 – 30 °C).
pH: For best growth, the pH of the tank water should be between 6.0 – 8.0.
Hardness: Riccia fluitans can thrive in very soft to moderately hard water comfortably.
Lighting:
The position of plants should dictate the intensity of lighting to be supplied.
Floating on the surface of the water can easily cope with low – moderate lighting.
Submersed Riccia fluitans will appreciate stronger lighting. Bright illumination is required to witness the full growth potential of this liverwort. Therefore, you should provide medium-high lighting (30-50 PAR) using an efficient lighting system.
Nowadays, a LED light fixture is the preferred choice because of its proven durability, efficiency, less heat generation, and better customization.
The target for this plant should be a minimum of 10 hours of light supply on a daily basis.
Read more about it in my article “Advanced Guide to Planted Tank Lighting”.
Substrate:
The choice of the substrate doesn’t really matter, after all this species is a famous floater which is also capable of growing fully submerged in the water column.
Whether plain washed gravel, sand, or soil, this plant will survive, just make sure to dose fertilizers to enrich the tank water.
CO2 and fertilization:
CO2: Once again, when we are talking about CO2, it depends on the position of Riccia fluitans in the tank.
As a floater plant, the Crystalwort has unlimited and constant access to carbon dioxide (CO2) that they use for photosynthesis and growth accordingly. Therefore, in this case, CO2 is not needed.
However, if kept underwater, it will look best with pressurized CO2 injections. Otherwise, the plant will look flaccid. That is why for submersed growth CO2 injection is recommended.
Fertilization: The addition of fertilizers can impact the growth and development of aquarium plants, especially those that absorb nutrients through the leaves.
Riccia fluitans needs a steady of liquid plant fertilizers, and this should be added directly to the water column. Plant fertilizers rich in essential macro and micronutrients can make a significant impact on the health and mass of your plants.
The plant will remain relatively skinny if water column nutrients are low.
Important: If you keep shrimp in the tank with Crystalwort, I would highly recommend reading my articles:
CO2 in a Planted Tank Guide
CO2 in a Shrimp Tank
How Copper Affects Dwarf Shrimp
Shrimp Safe Plant Fertilizers
The point is that a high level of CO2 and Copper (most fertilizers contain copper) is extremely dangerous to the shrimp.
Care and Maintenance of Crystalwort
Crystalwort is undemanding and fantastically beautiful. It will grow like crazy if you meet the conditions for its care.
Being able to thrive in a wide range of water conditions, with or without CO2 supplementation (depending on the position) is a huge plus.
Riccia fluitans grows fast, so it’s important to cut back the foliage with pruning scissors (link to check the price on Amazon) to curtail overgrowth. The shoots tend to grow towards the surface when they are not clipped often, and the outcome is not desirable.
Water flow should be low, the plant comes from quiet, slow-moving waters, so it’s best to provide little currents in your aquarium.
Due to the plant’s soft, fragile structure, the stems get to snap easily when there is a lot of water movement in the tank. If you don’t want to witness tiny loose pieces of Crystalwort floating around the tank, then you should keep slowing water currents.
Make sure to carry out routine partial water changes to reduce excess nitrates in the tank water. Also, prune the shoots frequently to maintain healthy and compact green vegetation.
Provide ample lighting, the light should be bright enough to penetrate the water column and reach the submerged lawns. For floaters, keep the plants in check to avoid casting too much shade in the aquarium.
The plant can thrive in the presence or absence of CO2, but CO2 in conjunction with liquid fertilizers rich in nitrates, phosphates, potassium, and iron will give the plants an extra boost.
From observation, tiny oxygen bubbles will start to form on the leaf tips when optimal growth conditions exist— this phenomenon is termed “pearling”.
Riccia is a floater that has to be tied down or glued to stay down as it does not attach to things, though most people like it as a mat or ball. It’s often netted down. Once it gets very full, the stems tangle together so it’s like a solid mass of the plant, but no roots.
Planting and Propagation of Crystalwort
Before planting Crystalwort, you must have reached a decision on whether to allow it to float on the water surface or to cultivate it submersed.
Floating it is easy, just split the plant into several pieces, spread them on the water surface, and watch them grow!
On the other hand, planting it completely submersed is a different ball game. Here, you have to divide the clump into small portions, attach it to a chosen object, and place it into the tank.
For instance, if you have rocks— drop a sizeable quantity of Riccia fluitans onto the rock, spread it to form an even layer, get a fishing line and an aquarium-safe glue. Now, glue one end of the thin fishing line beneath the rock, allow it to dry, then tie the fishing line all over the surface to secure the plant firmly.
Tie it properly to keep the vegetation in place to avoid detachment, make a final knot or affix the remaining piece of the fishing line to the rock with the super glue.
Repeat this for as many rocks as you want, the process can also be used on driftwood, slates, or coconut shells to attain thick mats on the bottom of the aquarium. Ensure the plant is attached properly, then rinse it in running water to get rid of loose pieces before placement.
Another way is to sandwich it between 2 pieces of mesh and let it grow through (like moss).
You can also take a net (for example, a hairnet), place Riccia on a rock then pull a hairnet over it. The plant will grow right through and over it hiding it from view.
Related article:
Propagation
The plant propagates through spore production but that is uncommon in the aquarium. Usually, any portion of the plant’s stems that breaks away is capable of forming a new plant.
To make things easier, take a sizeable amount of the plant, divide it into smaller portions and replant them in the tank following the outlined approach.
Crystalwort and Dry Start Method
One of the methods of growing Riccia fluitans is a Dry Start Method. This method will provide unlimited CO2 without any need to buy anything!
Moreover, it allows growing the plant even before cycling the tank.
- Instead of immediately filling the tank with water after planting, we only need to add enough water to reach the surface of the lowest part of our substrate.
- Place the plant on top of a substrate.
- Cover the top of the tank with cling wrap to increase the humidity.
- In about 3 or 6 weeks you can flood the tank.
Read more about “How to: Dry Start Method”.
Problems Associated with Crystalwort
Clogging the filter intake: Due to the structure of the Riccia it often breaks away and ends up clogging the filter intake. So, the plant should be always under control.
Fast growth: Riccia fluitans is characterized by an explosive growth rate. It grows and reproduces rapidly once the nutrient levels are high. In most cases, you may witness the overgrowth of Riccia fluitans in the aquarium. It can cover the entire surface and may be difficult to control.
Attachment: This plant does not attach to anything, unlike most mosses and liverworts, or even ferns. if it is not tied down, it turns into a complete mess.
Discoloration: Another issue is the melt and discoloration of shoots which is typically caused by a lack of essential nutrients in the tank water or poor water quality.
Keep in mind that neglecting trimming of the vegetation will encourage rot of the stems at the lower levels, so endeavor to trim the plants regularly.
You can also read “How to Spot Nutrient Deficiencies in Aquatic Plants”.
Benefits of Crystalwort
Aquascape: Riccia fluitans is one of the great choices for aquascapes. It forms a gorgeous and lush green carpet that complements the aesthetics of an aquarium.
Oxygenation: Helps to generate a lot of oxygen in the tank water.
The plant has a distinct feature which is the production of small pearls or bubbles of oxygen that stays on top of the plant, this adds a very lively aspect to the carpet.
Outcompetes algae: Under optimal conditions, Riccia fluitans grows so fast that doesn’t leave any chances for algae growth. This plant helps to effectively reduce the growth of algae.
Hiding place: Serves as cover and shade for inverts and small fish. It serves as a perfect hiding place for shrimp and fish.
Foraging place: Acts as a buffet of biofilm, which is an ideal first food for newly hatched fry and shrimplets.
Reduces excess nutrients: Fast growth rate of Riccia fluitans can also greatly benefit any tank because it will absorb phosphates, nitrates, ammonia, and toxins in the tank. Thus preventing the accumulation of harmful chemicals.
Crystalwort and Tankmates
Most varieties of community fish are ideal tankmates, including and not limited to the following species:
- Fish (for example, Bettas, Tetras, Zebra Danio, Platies, Guppies, Endlers, Mollies, Otocinclus Catfish, Pygmy Cory Catfish, etc.)
- Snails (for example, Japanese trapdoor snails, Ramshorn snails, Nerite snails, Malaysian Trumpet snails, Black Devil Snails, Asolene spixi, Rabbit Snails, etc.).
- Dwarf Shrimp (All varieties of Neocaridina (Red Cherry Shrimp, Blue Velvet Shrimp, Snowball shrimp, Black Rose, Orange Sakura, Green Jade, Rili Shrimp, etc) or Caridina species (for example, Crystal Red Shrimp, Caridina cf. babaulti, Blue Tiger Shrimp, etc.), Amano shrimp, Ghost shrimp, Bamboo shrimp, Vampire shrimp, ). Basically, you can keep any shrimp species with it. They will love it!
- Crayfish and crabs. It can be very hard to keep these animals in planted tanks. Most species will try to uproot and eat everything until they turn your beautiful tank into a wasteland. That is why floating plants will be a good choice for them. They simply won’t be able to get them, so you should have a problem.
Avoid
However avoid species that may find Riccia fluitans palatable, e.g. like Koi fish, Goldfish, Oscars, Rainbow, Jack Dempsey, Clown loaches, African Cichlids.
These species can really cause problems in the planted tanks.
Buying Crystalwort
This species is affordable and readily available, it can be purchased at local fish stores for a few bucks, usually $5 – $10 for a decent sized clump.
Also available is the tissue culture variant which comes in a small plastic cup, this variant is often devoid of algae and tiny snails. Regardless of the type, ensure that the plant is in a good condition to encourage growth when planted in the aquarium.
Quarantine Crystalwort
Do not forget to quarantine Riccia fluitans before putting it into your aquarium if necessary! For example, there is no need to do that if these are “in vitro” plants, it means that they are cultivated on nutrient media under sterile, laboratory conditions. In all other cases:
- The plant can have parasites, pests like snails, or even predators (dragonfly, damsefly nymphs, etc.).
- It could also be treated with chemicals (pesticide) to remove parasites, snails, etc. However, these chemicals are extremely poisonous to fish, shrimp, and other invertebrates.
To find out more, read my articles:
How to Remove Snails from a Shrimp Tank.
How to Quarantine and Disinfect Aquarium Plants.
Pesticides in Shrimp Tanks. Plants Quarantine.
In Conclusion
Riccia fluitans is an excellent choice if you want to attain lush green cushions on the foreground and midground of your freshwater aquarium at minimal costs.
Depending on how you cultivate this liverwort species, it can form thick mats on the water surface, water column, or aquarium floor. These dense mats are beneficial to shrimp and juvenile fish, they also absorb nitrates in the aquarium water, and serve as breeding spots for fish species.
Riccia fluitans is one of the easiest plants for high-tech setup (lots of light, CO2, etc.), however, I would not recommend it if you’re going for low maintenance.