The name “mosquito fern” arose from the belief that populations can grow so densely on the water surface that mosquitoes are unable to breed. Mosquito fern species in Asia have been used for this purpose, but although it might make it more difficult for mosquito larvae to breathe, it does not completely suppress them.
Mosquito ferns can become overabundant and should not be introduced. In some areas of the southern United States, mosquito ferns have interfered with livestock watering, blocked pump inlets, and affected commercial fishing. Also, because it can fix atmospheric nitrogen, it can enrich the water and encourage overgrowth of algae.
Mosquito ferns of various species have a tremendous value in agriculture. Because water fern species can capture nitrogen from the air and convert it to a form plants can use for nutrition, and because it can grow so abundantly, some species of Azolla are cultured as a “green manure” in rice paddies in southeast Asia. The paddies are flooded and the mosquito ferns introduced. Then, the fast-growing, thick mats of mosquito fern suppresses weeds, and when the mosquito ferns rot, the nitrogen fertilizes the soil. In China, this practice has been used for more than 1,000 years.
The relatively high protein content of dried mosquito fern inspired feeding studies on using it as a component in commercial livestock feed.
Azolla plants are sometimes used in aquariums. However, it is not as commonly used as duckweed, hornwort, crystalwort (Riccia, a type of liverwort), and several other floating plants that require less light. Remember, never release aquarium plants, fish, or invertebrates into natural waters.
The complex reproductive biology and structures of mosquito ferns can seem either mind-numbingly tedious or intensely fascinating, depending on your perspective. Many people love solving riddles and learning about weird, offbeat, nerdy topics.