The interaction of an organism that produces cytolytic substances (APONINs) toward the Florida red tide organism,Gymnodinium breve,is considered through computer modeling. Specifically, the interaction ofNannochloris oculatawithG. brevewas reviewed through the use of differential equations and a computer program called TK Solver 3.32. The differential equations that define the growth of the APONIN producing organism are matched with the differential equation associated with the growth ofG. breveand the rate of cell lysis to predict the interaction pattern and the time required for effective treatment. Obviously, certain boundary conditions or assumptions are involved and these are reviewed in detail. Under the conditions used, the model shows thatN. oculatawould eradicate aG. breveoutbreak in a little less than two days.