Sea grapes or green cavier (Caulerpa lentilifera), a common tropical green seaweed, consisted of polysaccharides to be used as a prebiotic precursor for prevention of pathogens in aquatic animals. The efficiency of polysaccharides extracted from sea grapes for prebiotic properties was conducted by comparing the growth of probiotic bacteria Bacillus subtilis at different concentrations in co-cultured with pathogenic bacteria Vibrio parahaemolyticus, a gram-negative motile bacterium that inhabits marine and estuarine environments throughout the world, causes of violent diseases outbreak in aquatic animals. The experimental research was 4 treatments with 4 replications including control group (LB broth), extracted sea grape enrichment in LB broth at 0.5, 1.0 and 2.7 mg. C/l. The result showed that the highest growth of probiotic bacteria appeared significantly at extracted sea grape in LB broth with 0.5 mg. C/l (1.64× 107±6.04× 106 cfu/ml). The said concentration was used as benchmark to clarify the pathogenic resistance. The comparison between monoculture of probiotic bacteria and co-culture of probiotic bacteria plus pathogenic bacteria indicated that there was non significantly different in growth of the bacterias. Hence extracted polysaccharides from sea graps (C. lentilifera) had potential to be utilized not only as a growth enrichment of probiotic bacteria but also inhibiting pathogenic bacteria.