Crystalworth (Riccia Fluitans)

Type:Floating Plant
Origin:Japan, East Asia
Growth Rate:Fast
Light Demand:Medium to High
CO2 Demand:Moderate


Riccia fluitans also known as crystalwort, or floating crystalwort is a freshwater plant that grows to about 2,5 cm long threads. It is a cosmopolitan plant, but the strain that can thrive fully submerged originated from Japan. In its natural habitat, it widely exists floating around in the ponds and slow-moving streams.

Conditions and Details


Crystalwort can be used as a free-floating plant or attached to surfaces such as rocks, logs, or driftwood in the aquariums. For keeping it submerged, it is recommended to trim the plant regularly (it grows in a ball-like shape) due to its fast growth. Otherwise, it will grow in long threads that some parts will detach from the main body and become free-floating over the water surface. Since it grows so fast, this plant can also be attached to mesh to create a carpet or a wall.

Riccia fluitans don’t have a root structure (like moss), and many hobbyists will tie the plant down with fishing string or thread to prevent it from floating while using submerged.

The optimal temperatures for Riccia fluitans range from 15-30 °C, and a pH value of 6.0 to 8.0 is appropriate for the plant. That wide range of conditions it can adapt makes it suitable to keep together with different types of fish.
Crystalwort doesn’t require a specific substrate to survive; it absorbs the nutrients through the leaves and stems. Nutrient-rich slow-flowing or still water is everything it needs to do just fine.


When it comes to lighting, it depends on the location of the plant in the aquarium. If the plant left free-floating it wouldn’t require much light, but on the other hand, if crystalwort is attached to a surface at the bottom of the aquarium, it will require more lighting. Insufficient light can cause browning to the plant, and eventually, it will die. CO2 injection promotes growth but, it is not necessary since riccia fluitans grows very fast.

Besides CO2, other nutrients that are beneficial for the crystalwort are nitrate, iron, phosphate, and potassium. Therefore, adding liquid fertilizer, especially when the crystalwort is emersed at the bottom of the aquarium, will benefit the plant.

The most necessary nutrient among others is nitrogen. Riccia requires high amounts of nitrogen to grow well, and when it is available and supported with proper lighting it can easily cover the aquarium surface or the area it is attached to. Aquarists widely prefer riccia due to the capacity of eliminating high amounts of nitrogen. It helps to remove the nitrogen from the water column and inhibit green algae growth in the aquarium.

Especially in heavy bio-loaded aquariums, the use of riccia fluitans will help to remove the excess nitrogen and phosphate and make the water more suitable for the livestock. Such as other floating plants, when it grows heavily on the surface, it covers the surface and prevents emersed plants from obtaining enough light. Thus, in planted aquariums, it is necessary to frequently remove riccia fluitans partially to enable other plants to receive enough lighting.

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