Diatoms take part in the initial process of fouling i.e. primary film formation. In order to understand the growth of the diatoms under different salinity conditions in the laboratory, this work was undertaken. Fouling diatoms on glass slides were incubated under three different salinities i.e. 15‰, 25‰ and 35‰o Totally 21 species of diatoms were incubated, and the following 12 species were found to show better growth : Amphora turgida, Biddulphia obtusa, Bacillaria paradoxa, Cocconeis littoris, Cymbella gastroides, Gramatophora marina, Licmophora gracilis, Navicula inflexa, N. oblonga, Nitzschia longissima, N. longissima var. closterium and N. sigma var. regidula. A maximum growth rate of 6105 cells / day was recorded in Navicula inflexa in 15‰ salinity. The species such as Navicula, Amphora and Biddulphia grew well in all the above salinities while Cymbella and Bacillaria preferred 15‰. Generally the diatoms on the glass slide, which were not healthy, did not grow after incubation. The growth of the diatoms was also found to be satisfactory at higher salinities of 25‰ and 35‰. Interestingly, diatoms which were not incubated also developed on the glass slide and this would possibly be due to the spores of such diatoms.