Crystalwort (Ricca fluitans): Complete Care Guide

In Aquatic Plant Care 0 comments
Castle Dawn Aquatics CRYSTALWORT (Ricca fluitans) Complete Care Guide

Crystalwort (Riccia fluitans) reminds me of a product that would be sold on those ‘’As seen on TV’’ infomercials show that would appear on television at about 3 am in the morning. ‘’What have you got there Bob?’’ ‘’Well, let me tell you Irene it’s called Crystalwort, you can grow it in substrate! You can grow it on hardscape! But wait there’s more! That’s right! You can even grow it floating!”.

Crystalwort is an aquascapers best friend as it can be used in multiple ways to help create stunning aquascapes. It is also commonly used with fish breeders, ourselves included, as it successfully keeps newborn fry safe when Crystalwort grows at the surface.

Crystalwort (Riccia Fluitans) Summary

Difficulty Level:



America, Asia and Europe





Common Names:

Riccia Fluitans, Riccia Moss, Crystalwort

Scientific Name:

Riccia Fluitans

Maximum Growth:


Growth Rate:


pH Level:

pH 5.5 – 7.5


20 – 26 °C (68 – 79 °F)

Aquarium Placement:

Midground, Foreground, Floating


Moderate to High


Spores or Propagation

CO2 Required:

Medium CO2 requirement: 6-14 mg/L. 



Crystalwort belongs to the Genus Ricca which has over 138 different species, and remarkably Crystalwort is the only species that are aquatic.

Crystalwort can be found in many parts of the world and has been a favourite among fish breeders since the early 70s. When Crystalwort was grown as a floating plant the dense clumps created a labyrinth structure that allow free-swimming fry to escape from any potential predators in the aquarium.

Crystalwort although popular with fish breeders was not that common in the hobby itself as an aquarium plant. However, it shot into fame when it was used by the inspirational Takashi Amano in the 90s. 

Thailand, Europe, and Singapore each have their own strain of Crystalwort. However, only the Japanese one can totally submerge. Takashi Amano pioneered the usage of Crystalwort in tanks. He was the first to completely immerse it, which was only possible due to his usage of the Japanese variety. Since becoming one of the more popular aquascaping plants in the aquarium hobby.


Crystalwort (Ricca fluitans) Variants

Castle Dawn Aquatics CRYSTALWORT (Ricca fluitans) Complete Care Guide Close Up of Ricca fluitans variants.

Dwarf Crystalwort (Ricca fluitans) sp.

The stems of the dwarf variety are shorter and a little bit thicker. It is also known that dwarf Riccia Fluitans sp. needs more light and CO2 to grow well. It grows more slowly than other Crystalwort variants, and it requires more light. Because they need a lot of light, dwarf sp. variants are usually planted higher up in the aquarium or added to the aquarium as floaters.

Slender Crystalwort (Ricca fluitans).

In this case, the name says it all: Slender Crystalwort (Ricca fluitans) has long, thin slender stems, which is how it got its name. It is the most common type in the aquarium trade and also grows the fastest. It doesn't need as much light as dwarf Crystalwort, so it's perfect for growing on hardscape and making Ricca carpets.


Spiny Crystalwort (Ricca fluitans).

Spiny Crystalwort ( Ricca fluitans), is native to Thailand and is less common in the trade than the other variants of Crystalwort. It does better in the aquarium when it can float than being fully submerged. It grows fairly quickly, and its spines make it great for breeding tanks because it makes a maze of structures as it clumps together, making it ideal for fry to retreat to.


Crystalwort (Ricca fluitans) General Care

Castle Dawn Aquatics CRYSTALWORT (Ricca fluitans) Complete Care Guide

Crystalwort is a low-maintenance aquarium plant and is suited for aquarists of all levels of expertise. It can be a beautiful, eye-catching element of any aquarium if properly cared for. Crystalwort, despite its appearance and growth characteristics, often referred to as moss is in fact a plant.

Crystalwort grows in a lot of different locations in the world because it can handle a wide range of environmental conditions, making it a bit more forgiving to beginners' mistakes. As a floating plant, it doesn't need a lot of light nor does it need CO2 to grow. But when it is grown fully submerged and tied to aquarium hardscape such as wood or rocks, the Crystalwort requires CO2 injections and a lot more light. 

It thrives in tanks with a gentle water flow, similar to its natural habitat. It is worth noting that the gentle flow on Crystalwort will encourage growth, however, be careful as too strong of flow will shatter its delicate stems.


Water Parameters:

Crystalwort is content in hard or soft water. In the wild Crystalwort is most commonly found in soft water areas with a pH of around 6.5. From personal experience, although the species is tolerant of an array of water conditions keeping the species at a pH of above 7.5 tends to stunt the Crystalwort growth.

In the aquarium keep Crystalwort in water with a pH between 6.0 and 7.5, carbonate hardness between 0 - 21°dKH and a general hardness of 0 - 30°dGH.

PRO TIP: When conditions are right for growth, tiny oxygen bubbles will start to form on the leaf tips. This is called "pearling."



Crystalwort is comfortable in temperatures between 20 – 26 °C (68 – 79 °F), and won't be bothered if the temperature needs to be risen or dropped outside of the temperature parameters, particularly if the aquarium has succumbed to an illness.



The lighting needs of Crystalwort are influenced by the location of the plant in the aquarium. It will demand more aquarium light if it is grown at the bottom of the tank than if it is grown on the tank's surface. 

On the surface, low-level lighting is more than acceptable; and depending on where Crystalwort is placed elsewhere in the aquarium, a high-level LED light, is recommended. 

Castle Dawn Aquatics has a vast range of aquarium LED lights perfect for Crystalwort (Ricca Fluitans).

We offer a vast range of aquarium LED lights perfect for lush Crystalwort growth.


The rule of thumb for successful Crystalwort growth is 2.5watts per gallon. For beginners to calculate your watts per gallon, simple divide the wattage of your aquarium light by your aquarium volume.

For example, a 20-watt aquarium light divided by an 8-gallon aquarium = 2.5watts per gallon.


CO2 Requirements:

As a general rule, it is best to give pressurised CO2 injections to submerged Crystalwort. Crystalwort regardless of the variant, can not survive in the long run without additional CO2 when it is submerged. Crystalwort that grows on the water's surface has easy access to more than enough CO2  so does not require injected CO2.

Submerged: Additional CO2 needed.

Floating: Will thrive without it.



Like all bryophytes, Crystalwort doesn't have vascular tissue. Instead, they absorb and diffuse nutrients and water. So, the substrate does not make a difference in its growth one way or the other. Save the money on expensive nutrient-rich aquarium substrate and put the money towards good aquarium lighting, your Crystalwort will thank you for it!



A good fertilizer is a must when keeping Crystalwort in the aquarium, particularly if the plant is submerged. A fertilizer containing a good source of nitrate, phosphate, iron and potassium will help keep your Crystalwort lush and healthy.

NOTE: There have been reports that the use of EXCEL can cause bleaching of Crystalwort and the death of the plant.


Common Problems

 Submerged Crystalwort (Riccia fluitans) Turning translucent (Ricca Melt)

 This problem as common as it is can be caused by multiple factors


Ricca mat has become too dense.

When the Crystalwort mat becomes too thick the bottom of the Crystalwort becomes starved of light. Crystalwort is very light-dependent for CO2 exchange, if parts of the plant do not get enough light it will gradually turn translucent and die.

Keep your Ricca mats well-trimmed to allow light to penetrate the lower parts of the plant, this will prevent the Ricca mat from dying and the plant disintegrating.


Crystalwort is not getting enough nutrients

Crystalwort requires extra nutrients when submerged to thrive. If your Crystalwort begins to fade and growth has been to a minimum, there is a high chance that the Crystalwort is not getting enough nutrients.

Use a good liquid fertiliser in the aquarium that is rich in Kno3 (Potassium nitrate). This will give your Crystalwort the boost it needs.

Do NOT use more than the recommended dose, overfeeding of fertiliser can cause damage to Crystalwort.


Chemical damage

Crystalwort is very sensitive to aquarium chemicals, even some chemicals that are made for aquatic plant health. If the product is known to damage Vallis ( Vallisneria sp.) it will certainly harm Crystalwort. This includes most algae treatments for the aquarium, including hydrogen peroxide.


No CO2 And Low Light

I'm sure if you search the online forms you will find aquarists who are keeping Crystalwort without CO2 and using low light. To them, we tip our hats, but for us, CO2 and good LED lighting are the main ingredients to success when keeping Crystalwort submerged.

Without CO2 and good LED aquarium lighting, in our experience, submerged Crystalwort turns pale and withers away, and either of these two components is the main cause of Crystalwort melt.


Foliage Maintenance

Crystalwort is predominantly fast-growing with the exception of the dwarf sp. variant. If Crystalwort is left to its own devices it can grow out of control without regular maintenance. Regularly use trimming as a way to guide your Crystalwort in the direction you want it to grow, as it naturally grows wildly and quickly.

PRO TIP: Turn off your pump before trimming Crystalwort or you will find it tangled in and around other plants in your aquascape for weeks to come.


Propagation (Breeding)

Castle Dawn Aquatics CRYSTALWORT (Ricca fluitans) Complete Care Guide Propagation.

Our volcanic rock planters are ideal for creating Crystalwort carpets.


Crystalwort in the aquarium is very simple to reproduce, and it will actually do it on its own and prolifically at that, by releasing spores from the tops of its stems that will float away and form new branches. If you wish to take matters into your hands then simply cut branches or pull clumps from the parent plant and WOLLAH!, new plants!


Is Crystalwort right for you?

Crystalwort is a stunning aquatic plant that is adaptable and asks for little in regard to care. All it asks is, ''if you submerge me feed me and if you float me well ... leave me alone.'' It can be grown on nearly every type of aquarium hardscape and used to create breathtaking Ricca carpets or even walls. It sparks the aquascapers creativity with its endless growth opportunities and for this reason, it is why it has become such a beloved plant in the fishkeeping community.


We hope you enjoyed and found this article useful. If you have any further questions about Crystalwort (Ricca fluitans) care please leave them in the comment section and we will get back to you.

The article was written based on personal knowledge and experience in keeping the species. It may differ from your own experience or opinions of the species.

Disclaimer: All images are credited accordingly, if an image is miscredited please contact us at


Leave a comment

Your email address will not be published. Required fields are marked *

Please note, comments must be approved before they are published