The function of the bag is to contain and protect the fish and to provide a marine habitat. The net is normally flexible and made of synthetic netting of nylon or polythene fibers reinforced with polythene ropes, although recently new stronger materials like Spectra or Dynema have appeared. The nets are kept stretched vertically with weights at the bottom of the cage or fastened by rope to the framework depending of the type of cages. Rigid cages made of metal netting (galvanized mesh, copper-nickel mesh or vinyl-coated mesh) mounted on rigid metal frameworks also are used. The flexible net bag is most used due to cost.

Antifouling Paint

Marine bio-fouling causes many problems for the aquaculture industry. Colonisation of infrastructure by marine life can cause asset degradation, leading to costly maintenance and/or replacement. Bio-fouling can also impact on the health of the stock as fouling organisms can reduce flow of water through nets, remove vital nutrients from the water and reduce the amount of oxygen available.

One method of controlling bio-fouling is through the use of anti-fouling coatings. The coatings available to aquaculture are often adapted from other commercial uses and have decreased levels of biocides to make them suitable for use with aquaculture species. Antifouling paint is ideal for the treatment of fishing and farming nets to prevent them from drying, to protect them from sun beams and abrasion, to reduce bio-fouling and facilitate maintenance.