TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Virus: In (I), the algae is Chaetocerous salsugineum. (I) lacks tail and outer membrane, and has a particle size of 33-4 nm, and is in globular form.Preferred Method: In (M2), the cultivation step is performed at 15 degreesC, and the method is performed at an optical density of 100-150 micronsol photons m-2s-1, in dark and light atmosphere. In (M3), the virus is embedded to a fixed agent. (M1) involves dispersing the virus in red tide water area by embedding in a nori-seaweed culture raft into bottom waste sludge. ACTIVITY - Algicide.    MECHANISM OF ACTION - None given.    EXAMPLE - Test mud sample (12 g) was mixed with SWM3 culture medium (12 ml), stirred well for 30 minutes at 400 rpm. The contents were centrifuged at 4 degreesC for 10 minutes by 2000 rpm. About 0.2 ml of the centrifuged supernatant liquid was inoculated into culture solution (0.8 ml) for Chaetoceros salsugineum Ch42 strain during logarithmic growth phase. Controls were also run simultaneously, using heat processed C.salsugineum Ch42 strain. Limiting dilution was performed for cloning algicidal factor. About 100 mul of the diluted liquid was inoculated to culture solution (150 mul) for Chaetoceros strain during logarithmic growth phase, and cultured for 14 days as above. The culture solution having algal dispersion from highly diluted samples was collected and inoculated in the culture solution for C.salsugineum Ch42 strain, to complete the cloning of algicidal factor. The obtained algicidal factor suspension was inoculated aspectically into ST 10-1 culture medium, and cultured for 1-2 days at 20 degreesC. The presence of the bacteria was confirmed by the cloudiness of the culture medium. The culture solution (in which algal dispersion is confirmed) was inoculated with virus. Titer of the virus suspension at the time of starting an experiment and after preservation was calculated by limiting dilution, and was compared. Transition of the cell density of C.salsugineum Ch42 strain at the time of inoculating algicidal factor clones CsNIV strain 21 was studied. The flush of a virus density was observed from 12th hour to the 24th hour after the virus vaccination. Results showed that reduction in cell density was remarkable from 36th hour to 76th hour after inoculation.