TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The type of unwanted living organisms includes rotifers, cryptomonads, larval copepods, gnathostomulids, monerans, and/or spirotrichs. The algae cultivation fluid includes algae of genus Nannochloropsis.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred System: The algae cultivation source includes at least one of a raceway reactor and a photobioreactor. The cavitation apparatus includes a venturi-type device having a convergent nozzle and a divergent nozzle and an apparatus throat extending between it.    TECHNOLOGY FOCUS - PHARMACEUTICALS - Preferred Method: The method (M1) further involves selectively varying the amount of cavitation to selectively control the amount of unwanted living organisms within the algae cultivation fluid; and selecting the amount of cavitation based upon the type of unwanted living organisms within the algae cultivation fluid. The apparatus throat includes at least one orifice of an orifice plate. The orifice plate includes a central orifice disposed in axial alignment with a central axis of the orifice plate and several intermediate orifices spaced apart from and disposed in an arcuate pattern around the central axis. The central orifices include a frusto-conical geometrical configuration having a sidewall disposed at twenty degree angle relative to the central axis of the orifice plate, further where at least one of the intermediate orifices include the same geometrical configuration as the central orifice. The apparatus throat includes a venturi throat of a venturi-type device, where the venturi throat is disposed between a convergent nozzle and a divergent nozzle. The method (M1) further involves causing the algae cultivation fluid to swirl before the algae cultivation fluid enters the convergent nozzle of the venturi-type device; executing the method according to a predetermined schedule; receiving the algae cultivation fluid from an algae cultivation fluid source and providing the algae cultivation fluid to the algae cultivation fluid source after the step of subjecting; diluting the algae cultivation fluid provided to the algae cultivation fluid source with a dilutive fluid after the step of providing; and re-subjecting the algae cultivation fluid to an additional amount of cavitation by passing the algae cultivation fluid through a second apparatus throat positioned downstream of a first apparatus throat. The method (M2) further involves: monitoring the amount of unwanted living organisms within the algae cultivation fluid to determine an appropriate time to perform the step of reducing; and diluting the algae cultivation fluid with an additional fluid to further reduce the amount of unwanted living organisms within the algae cultivation fluid. ACTIVITY - Fertilizer. No biological data given.    MECHANISM OF ACTION - None given.    EXAMPLE - No suitable example given.