Ceratopteris is an aquatic fern genus native to the tropics. In nature, these plants provide a source of nutrition and shade for organisms living in the water, in addition to purifying the waters they grow in. In cultivation, these ferns are used by aquarists for much the same purposes. People interested in growing Ceratopteris species in an aquarium or water garden can usually obtain specimens from a store specializing in aquatic plants. Other gardeners can also provide plants for sale or trade and because these plants tend to thrive in propagation, gardeners may be quite happy to have people interested in excess plants.
There are less than 10 known species in this genus, which falls under the group of ferns known as homosporous because they only produce spores of one size. They have evolved to live entirely underwater in tropical regions, where water tends to stay warm and can host a wide variety of plants and animals. The plants may float freely in relatively still water, or root in the substrate, and reproduce with adventitious roots and budding growth habits. Some specimens can grow quite large in optimal conditions.
Known by names like “water sprite” and “floating lettuce,” this genus was once used for food in some regions of the world. In addition to being cultivated by aquarists, it is also used in genetic research. Plants that are easy to grow in cultivation can be valuable resources for research and development and genetically modified versions of Ceratopteris are available for researchers in need of plants to work with.
Aquarists will need relatively warm water for cultivation, and should take care to rinse plants before introducing them to their tanks to reduce the risk of passing on disease, although Ceratopteris is usually a very hardy plant genus. The plants can grow in a variety of light conditions and thrive in water of various pH balances, allowing people to adjust tanks to meet the needs of more finicky residents without needing to worry about their Ceratopteris.
As these plants start to develop, divisions can be made from new buds and roots. The divisions can be passed on to other gardeners or discarded. If too many accumulate in a single tank, the plants can become crowded and unhealthy conditions may develop. These plants can withstand some nibbling by fish and other animal occupants of their environment, making them ideal choices for tanks where herbivorous fish are being raised.