The fish farming industry suffers significantly from the effects of biofouling. The fouling of cages and netting, which is costly to remove, is detrimental to fish health and yield and can cause equipment failure. With rapid expansion of the aquaculture industry, coupled with the tightening of legislation on the use of antifouling biocides, the problems of fish farm biofouling are increasing. The nature of the biological communities that develop on fish farm equipment and the antifouling practices that can be employed to reduce it are described here. Particular emphasis is placed on antifouling legislature and the future needs of the industry. The biological communities that develop on fish cages and netting are distinctive, in comparison to those that foul ships. Temperate species of particular importance, because of their cosmopolitan distribution and opportunistic nature, include the blue mussel Mytilus edulis and the ascidian Ciona intestinalis. Antifouling practices include predominantly the use of copper-based antifoulant coatings, in combination with practical fish husbandry and site management practices. The antifouling solutions presently available are not ideal, and it is widely accepted that there is an urgent need for research into combatant technologies. Such alternatives include the adoption of "foul-release" technologies and "biological control" through the use of polyculture systems. However, none of these have, as yet, been proven satisfactory. In view of current legislative trends and the possible future "phasing out" of available antifouling materials, there is a need to find alternative strategies.