Crystalwort, also called Floating Liverwort or simply Riccia, is a beautiful plant that makes any aquarium more impressive!
Since it is used by advanced aquarists, novices are often scared off, but wrongly so. This plant is quite undemanding and comes with so many benefits. Crystalwort or Riccia keeps down algae because its growing habits respond to the amount of available nutrients.
Using Crystalwort is also a great way to boost oxygen levels in the tank. If given enough Co2 and light, this plant will produce many small visible oxygen bubbles that will be caught in the intricate "leaves" until they are absorbed into the water. This is often called pearling and is quite beautiful. This plant is also great for breeding tanks both to catch eggs and to protect fry.
Crystalwort tends to be a naturally floating plant which can provide good cover for small fish and fry. However unlike other ferns and mosses, it does not tend to be self attaching. Everyone can find an anchoring method that works for them, but the most popular are use of either a plastic hairnet or fishing line. You may need to prune or retie the Crystalwort on occasion to be sure that light passes all the way through.
The most ambitious aquarists will attempt to anchor this floating plant down to form a carpet, a style piloted by Takashi Amano. In his book, Nature Aquarium World: Book 1, you can see many examples of Takashi's incredible use of Crystalwort to help create beautiful aquatic environments. He includes a description with photographs of his process as well as parameters for water quality, lighting, substrate, and more for each of his tanks.
One problem with Riccia is its tendency to pick up debris. But larger objects can quickly be removed with tweezers. Smaller particles can be removed by rinsing it in a fishnet.
For more Information on keeping a planted aquarium see:
About Planted Aquariums, Adding Aquatic Plants For a Healthy Aquarium
Crystalwort, also called Riccia or Floating Liverwort, has a huge geographic distribution. This plant can be found on nearly every continent.
Temperature: 59-86° F (15-30° C)
Light level: bright to extremely bright. (at least .5 watts per gallon)
The ends will divide forming an intricate crystalline structure (hence the common name Crystalwort). Just pull the desired amount out of the clump and new growth will fill in.
Crystalwort or Riccia is available in many specialized fish stores and online. Be exceptionally cautious that this plant is never released into the wild. It has been banned in some places, making it illegal to sell in those areas, because of irresponsible aquarists.