During the period of the Cochlodinium polykrikoides red tide occurrence in the southern coast of Korea in 1997, we obseved the vertical migration of red tide organisms in situ, along with environmental factors such as water temperature, dissolved oxygen, pH, chlorophyll $alpha$ and nutrients for practical application of loess suspension techniques ot diminish fisheries damage. To cope with serious outbreaks of red tide of C. polykrikoides, the finfish culturists resorted with loess suspension to disperse the bloom watermass by turning around it with fishing boats in full speed. Peak in afternoon the cell numbers were diminished in the surface layer after sunset red tide organisms settled down in the middle and bottom layer progressively again after sunrise. Chlorophyll $alpha$ and dissolved oxygen showed the same trends of variation with the cell number. In the course of controlling the red tide with loess suspension we could not find any severs oxygen deficiency to kill the culture species.