In this study, the coagulation and foam separation for collection of red tide phytoplankton Peridinium bipes in fresh water was examined in a batch system. The coherency ofP.bipeswas worse than other phytoplankton. During the treatment of P.bipessuspension by the coagulation and foam separation without pretreatment, the cells were difficult to catch in the iron hydroxide floc, and the recovery rate was low. By pretreating with ozone or UV, however, the coagulation and foam separation method was remarkably improved, and the recovery rate was above 90%. The adequate coagulant dosages of ozone and UV pretreating methods were 3mg-Fe/l and 5mg-Fe/l, respectively. The casein dosage was 15mg/l in each case. The ozone method was faster than the UV method. The ozone method was accomplished in only 9 minutes. Iron and casein chemicals were scartely detected in the treated water of the ozone method. As a result of the AGP test, in a control medium and the treated water of the ozone method, the significant difference could not be observed. In conclusion, ozone aeration is the appropriate pretreatment for collectingP.bipesby the coagulation and foam separation.