Cleaner water: The Agriculture, Fisheries & Conservation Department has placed 10 artificial reefs at the Sham Wan Fish Culture Zone to serve as biofilters to improve water quality.

The Agriculture, Fisheries & Conservation Department has placed 10 artificial reefs at the Sham Wan Fish Culture Zone to serve as biofilters to improve water quality. They can filter 6,000 cubic metres of sea water daily.

Fish faeces or unconsumed feed from fish culture activities can lead to a rise in water turbidity. This organic matter can accumulate in the bottom mud, increasing the possibility of oxygen depletion.

The specially designed biofilters provide hard surfaces that promote the development of numerous filter-feeding organisms which remove nutrients and suspended particles in the water.

Biofilters can also enhance marine life by providing shelter. Fish and marine life attracted to the biofilters may eat excess feed falling through the cage nets, reducing pollution in the fish-culture zones.

Similar biofilters placed at the Kau Sai Fish Culture Zone in 2002 have proved successful in improving the marine environment below as well as surrounding waters.