1) Fungus genus 2) Genus saprolegnia 
Saprolegnia is a genus of freshwater mould often called a `cotton mould` because of the characteristic white or grey fibrous patches it forms. Current taxonomy puts Saprolegnia as a genus of the heterokonts in the order Saprolegniales. ==Habits== Saprolegnia, like most water moulds, is both a saprotroph and necrotroph. Typically feeding on waste.....
(from the article `malachite green`) ...medicinally in dilute solution as a local antiseptic. Malachite green is effective against fungi and gram-positive bacteria. In the fish-breeding ...
[n] - aquatic fungi growing chiefly on plant debris and animal remains
saprolegnia A kind of aquatic fungi, the water molds.
genus Saprolegnia noun aquatic fungi growing chiefly on plant debris and animal remains