Apparatus for controlling algae and bio-organisms in bodies of fluids, such as water. The algae control system includes a power unit and a transducer unit that includes a sonic head that radiates in multiple directions. The power unit connects to various power sources, including a mains supply connection, a solar panel array, and/or a battery. The power unit is electrically connected to the transducer unit. The sonic head includes a driver and a transducer subassembly. The driver excites the transducer subassembly to emit ultrasonic waves at various frequencies in the water surrounding the sonic head. Emissions at a high density of frequencies are enabled by the transducers. The frequencies include the critical structural resonant frequency for each microorganism to be controlled. The power unit and driver each include a processor in communication with each other. The processors store and execute a program for a selected application configuration.