This family of ferns has no common name. Place your cursor over images to control them.

Mosquito Fern (Azolla)

Also known as duckweed fern, fairy moss, or water fern, this is one of a group of ferns that evolved into small water plants. Blooms of Azolla are signs of high levels of phosphorous in the water. While they're red like red algae, usually they're an aesthetic annoyance at worst. In fact, Azolla is economically important. In Asia it's co-planted with rice to provide that grain species with nitrogen. Also, the floating mats of Azolla limit the growth of weeds that might compete with rice plants. Mats of Azolla also have the reputation of making life difficult for mosquito larvae, hence one of its common names.

Azolla may have reversed a previous (natural) episode of global warming (see this Wikipedia article on the Azolla Event).  So instead of fretting about how Azolla is messing up your preferred aesthetic for water scenes, think of it as a superhero which we may need again.