Vibrio cholerae O1 was reduced from 40 per litre to zero after 5-10 days, and salmonellae from 130-470 per 100 ml to 1-2 per 100 ml after 13-16 days. Faecal coliforms were better indicators of these bacterial pathogens than were faecal streptococci or Clostridium perfringens, and FC numbers of 1000 per 100 ml were associated with an absence of V. cholerae and 1-2 salmonellae per 100 ml. In-pond survival studies indicated that significant removal of V. cholerae occurs when the sulphide concentration is ≥ 3 mgl-1, thus indicating the need to include anaerobic ponds.