The second step in the evolution of low pollution feed was reducing phosphorus to the minimum level required for fish health and growth. The third development was new technology that allowed high levels of fat to be included. This increased the energy density of the feed which reduced the amount of feed needed to grow a unit of fish. Optimizing the protein to fat ratio took several years. Recently it has become apparent that biochemical oxygen demand is the critical environmental waste product from cages.
Current research involves further reductions of biochemical oxygen demand.
The other feed related source of waste is uneaten feed. Farmers have enormous economic incentive to waste as little as possible. New technologies, such as underwater video cameras, are further reducing feed waste. Other Environmental Initiatives Aqua-Cage has tried to be environmentally friendly when the opportunity arises. Two stroke out-board engines have been replaced by four stroke engines.