B. subtilis BT23 showed a higher inhibitory activity than the other two Bacillus spp. tested. BT23 showed inhibitory activity against 112 Vibrio spp., V. harveyi (39 isolates), V. anguillarum (24 isolates), V. vulnificus (30 isolates) and V. damsela (19 isolates) obtained from P. monodon culture hatcheries and ponds (Table 1)