NOVELTY - A method (M1) of reducing an amount of unwanted living organisms and increasing an amount of biofuel producing algal cells within an algae cultivation fluid, involves: subjecting the algae cultivation fluid to an amount of cavitation, where the amount of cavitation is defined by a pressure differential between a downstream pressure and a vapor pressure, where the pressure differential is divided by half of a product of a fluid density multiplied by a square of a velocity of an apparatus throat; and cultivating the biofuel producing algal cells.    USE - For reducing unwanted living organisms and increasing biofuel producing algal cells within an algae cultivation fluid (claimed) used in the manufacture of biodiesel, bioplastics, dyes and colorants, fertilizers, animal feedstock, various pharmaceuticals, and nutraceuticals, and for controlling pollution.    ADVANTAGE - The method improves production of biofuel from algae cultivation fluid; removes competing algae species with flagella from the algae cultivation fluid during the cavitation process; and reduces unwanted living organisms that compete with the algae cells for food (e.g. minerals and inorganic chemicals) or directly consume the algae cells.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a system for reducing an amount of unwanted living organisms within an algae cultivation fluid, comprising: an algae cultivation fluid source for receiving and retaining an algae cultivation fluid; a cavitation apparatus in fluid communication with the algae cultivation fluid source; and a fluid motive source adapted to communicate the algae cultivation fluid from the algae cultivation fluid source into the cavitation apparatus with sufficient velocity to induce an amount of cavitation within the algae cultivation fluid by passing the algae cultivation fluid through the cavitation apparatus; and    (2) an improved method (M2) of producing a biofuel from algae cultivation fluid, involving: reducing an amount of unwanted living organisms within an algae cultivation fluid by passing the algae cultivation fluid through at least one apparatus throat to induce an amount of cavitation within the algae cultivation fluid to reduce the unwanted living organisms within the algae cultivation fluid, where reducing the amount of unwanted living organisms within an algae cultivation fluid causes algae cells within the algae cultivation fluid to mature at an accelerated rate relative to algae cells within algae cultivation fluid having a higher concentration of unwanted living organisms; separating algae cells from the algae cultivation fluid; and processing the algae cells in such a way that a biofuel is produced.