Azolla (Azolla sp.) is an aquatic fern consisting of a short, branched, floating stem, bearing roots which hang down in the water. The leaves are alternately arranged, each consisting of a thick aerial dorsal lobe containing green chlorophyll and a slightly larger thin, colourless, floating ventral lobe. Under some conditions, an anthocyanin pigment gives the fern a reddish-brown colour. Plant diameter ranges from 1-2.5 cm for small species such as Azolla pinnata, to 15 cm or more for Azolla nilotica. Azolla plants are triangular or polygonal in shape, and float on the surface of the water, individually or in mats. They give the appearance of a dark green to reddish carpet, except Azolla nilotica that does not produce the red anthocyanin pigment. The most remarkable characteristic of azolla is its symbiotic relationship with the nitrogen-fixing blue-green alga (cyanobacterium) Anabaena azollae. The fern provides nutrients and a protective cavity in each leaf to Anabaena colonies in exchange for fixed atmospheric nitrogen and possibly other growth-promoting substances

• Family Name : Salviniaceae
• Origin : Africa
• pH : 4.5-7
• Temperature : 18-26°C